Guardians, BF, Elder Wraiths' "glitched" KB intentional?

As for bf, if this is about the "strategy whatever plan" it only makes sense if timing your attacks was meant to be part of the game.

Except there's absolutely no visual cue that he's going invincible... he just does it before every time he attacks (and when KB'd ... and partway through attacking), and it looks like he's just standing there but suddenly you can't hit him. I've tried timing my attacks but the only time I can reliably hit is while he's jumping the air during the attack, and if he's being KB'd that doesn't work.