Same

Can confirm, was also just trying to tame one and encountered the same issue, guess it hasn't been fixed yet? Also while riding it you can attack but it won't damage or gather anything, and whistling another tame to follow doesn't work for more than a second. It's hella broken tbh.

Yo, just bumping this up with an answer: They are knockout tames, not passive tames.
I used extraordinary kibble for my phantom manta