Not quite sure what fallacy this would be.

Backgroud: 

In acts Acts 9:31 uses two words
καθ’ - prep
ὅλης - adj

Person A: Acts 9:31 If it was referring to a place or thing it would be a noun. neither of those word are nouns. so it can not be referring to a specific name of a church. That is just Greek grammar.

Person B: I do not need to learn Greek
For several reasons.
Here is 1.)
For almost 2000 Years every Trustworthy an Reliable Biblical and Historical Church Scholar has understood it to mean exactly what i noted.

Person B believes Acts 9:31 is the name of the church: Catholic church.

Not quite sure it would fit  appeal to authority or bandwagon.

Things get dicey with religion because dogma and faith often inform scholarship. For example, virtually every Catholic scholar will insist that Jesus was an only child, yet virtually all protestant scholars (and secular) understand that the Bible makes it clear that Jesus had siblings. When people choose their experts based on the conclusion they draw, this is showing confirmation bias. In addition, experts to conclude what they do based on dogma, faith, or ideology, are often making an appeal to false authority . I wouldn't say appeal to authority however, because there is no firm declaration that something is true or false; it is more of what a person believes.