How does the follower/following count work when there are mutuals that have been blocked?

Noticed this interesting mechanic, wanted to confirm if it indeed is the case. Suppose A has blocked B on instagram, and there is a third person C who is friends with A. Then when B opens C’s profile they either see (1) the true follower/following count or (2) the true counts minus 1.

But it seems like it’s (2) if the counts are small enough, and (1) otherwise. It doesn’t seem to matter either whether or not B can actually see C’s follower/following list (like if a public account, or a private account they follow)

The threshold might also be around 100.

Is this an actual thing? Or do I have cherry picked examples that have some other underlying reason?