I have had a couple of friends get most of the way through both BfA pathfinder achievements, only to then transfer realms and faction - yet they were still able to continue on with the reputations they had already earn and continue on with their achievement process.
I, on the other hand, did the same thing and tried to finish getting my pathfinder achievement, but then I noticed it wasn’t tracking most of the reputations I already had revered. I contacted blizzard about it and they said it should be a glitch and when I do the final part of the achievement, it should trigger and I should unlock BfA flying.
I went all the way through the rest of the achievement, and it didn’t trigger. So I contacted customer support about it and was told “it is intended for the achievement to not be obtainable if you transfer your character”.
This is ridiculous! Why can my buddies do it, and get flying. And then I’m TOLD I can do it by a blizzard employee, and then when I do it I don’t unlock the achievement, and then am told I need to completely restart.