Except Tarke was completely correct in this case but sure bud
Tarke was referring to supportability, which is a separate concept from tags. Specifically, that Burning Arrow is supportable by Less Duration support (because it has to be due to the threshold gem). None of that has anything to do with tags.
He had (and still has) a valid point that it's a weird situation with regard to supportability because of the threshold jewel, but tags have nothing to do with that, and at no time have such interactions been able to modify the tags on a gem. That simply isn't and never has been possible.