How many logical fallacies are present here?

I'm potentially restructuring the question, as was suggested by Dr Richards, so if you're still interested keep a look out for that.
Decision maker does state that it's to benefit group Z, but it's baffling as to how they came to that conclusion.

As for your last paragraph, my thoughts exactly - was the implementation bad? Was there some kind of miscommunication? I didn't give context because this is a real thing, but essentially, in the trust and safety department the decision was made to force all tabs to close on a laptop if the lid is shut (within group Z). Why? What does this achieve? If I close my laptop, and then re-open it, why can I not have all my tabs from 10 minutes ago still be there? Must I really spend many minutes re-opening every tab each time I close the laptop? This adds up to a large amount of time wasted each day.

Person 1 is concerned because he is directly affected.
Decision Y has no possible merit because there is no logical reason for it being put into practice; its only purpose is to provide some sort of benefit to the group of people (let's call them group Z) it is directed towards (such as person 1, who is part of group Z), and person 1 has observed that it only causes him inconvenience, and absolutely no benefit. It would also never logically provide benefit to any other member of group Z (hence my analogy) because all members of group Z have the same interests regarding the decision.
Decision Y causes many problems and zero benefits. Therefore, it only causes problems.
 The above statement seems like good logic. Am I missing something?

As for the statement about the burden of proof, in the discussion it is self-evident and agreed upon that members of group Z will all be very inconvenienced with no benefits available.
I can see where the misconception is here, I'll clarify.
Person 2 argued that while it's inconvenient for group Z, there might be some kind of benefit to the corporation in making the decision (much like how baby seal clubbers get the fur.) Person 1 states that this is not the case, and that a person typing up a document to change company policy does nothing except change the policy to whom the decision is concerned (group Z).
Person 1, knowing this, asks what kind of benefit to the corporation there could possibly be, having reasoned that there shouldn't logically be any. Person 2 can only make guesses like "it could save them money in some way", but these guesses are proven to be false.

And then please explain where the illogicality is on person 1's part...

You have added additional information that also needs substantiation. I suggest you rethink exactly what you want to ask, then resubmit the question.  

not entirely sure why i need to resubstantiate my clarification just because you didn't understand what I wrote, but I think I'll drop it now, I've lost interest to be honest

It is because I do not understand it that you should rewrite it. Critical thinking is hard work, and learning how to do it requires an education. Critical thinking is not automatic. 

If achieving knowledge is the goal of thinking, then effective thinking must use tools that achieve the goal reliably. Knowledge is justified belief.
Beliefs amount to expectations about what is, or likely, to happen.
True, or correct, beliefs are expectations that are consistently fulfilled under similar circumstances.

Thinking involves making sense of what we observe, figuring out the consequences of what we do, and weight our options to which are reasonable and well grounded. Emotions or feelings are not thought. 

Effective thinking, sometimes called critical thinking, is the primary method to arrive at true (i.e., correct) beliefs. Children are not born with the power to think critically, nor do they develop this ability naturally beyond survival-level thinking. Critical thinking is a learned ability that must be taught. Most individuals never learn it. Critical thinking cannot be taught reliably to students by peers or by most parents. Trained and knowledgeable instructors are necessary to impart the proper information and skills. Math and science instructors have precisely this information and these skills. 

The natural tendency of thinking is to support a view arrived at by other means. ~~Edward de Bono.

In the first chapter of his book “de Bono’s Thinking Course,” Edward de Bono describes the “Intelligence Trap” and devotes a few pages to the subject. He says, “Highly intelligent people may turn out to be rather poor thinkers. They may need as much, or more, training in thinking sills than other people.”

Yes, restating your question would be a good exercise for you --- even if you do not resubmit it.

You know what - you're right. Restructuring it would be a good exercise.
Shall I post it as a comment or make an entirely new question?

I say new.

https://www.logicallyfallacious.com/questions/r6zniOfF/redraft_of_how_many_logical_fallacies_are_present_here.html

Is it still the argument from ignorance if:
Person 1 evaluates that it's unlikely that a good reason for decision Y exists (due to good reasoning), but rather than drawing the conclusion that no such reason could possibly exist, instead draws the conclusion that it's just unlikely that a good reason exists, and that if it does it's likely to be weak?
It's like how you said: " So, it is possible sometimes"  ... the possibility always exists. The extent of the probability depends on the situation, and in this one, it's extremely unlikely.

No, in that case I don't believe it would be argument from ignorance. You can present your arguments and based on that argumentation conclude that something is improbable. I would describe that as informed opinion or less informed opinion depending on the degree of how sound the arguments are, but definitely not argument from ignorance.