Yes, but not while observed directly (the way I read it).
The word "though" is a problem for this interpretation.
You're being disingenuous.
No, I'm not.
I assume that what Crawford meant was the ambiguous statement he made,
I don't think the statement is (intentionally) ambiguous. I think he assumed readers would perceive that the word "though" between two claims is intended to contrast those claims, and he contrasted "can't hide while being observed" with "can hide while being observed if you have one of these two abilities which have no purpose but to allow you to transition from unhidden to hidden while being observed".
The problem is, your "ambiguity" relies on never, ever, looking at the whole claim at once. When we're talking about hiding while directly observed, you say "oh, but it could mean remaining hidden". When the word "vanish" is pointed out, you jump to "oh, but it could mean while not being observed". But we're talking about a single thing being given as an example; vanishing while being directly observed.
But... Why would you ask him to "nullify the ambiguity"? You wouldn't. You'd ask him to confirm that he intended that ambiguity, and if he said "yes, I was trying to be ambiguous there", you'd win, and if he said "no, it absolutely meant that these powers allow a character to transition from unhidden to hidden while being directly observed", you wouldn't.
And I have drawn the obvious inference that you think he'd answer the same way I think he'd answer, by confirming that there was no intended ambiguity. Conveniently, if I'm wrong, it's stunningly easy to demonstrate that I'm wrong.