The play in question can be viewed here https://www.youtube.com/live/-da5_KWvqlU?si=fa5i26s_JH-XED4i&t=1932 (at 32m12s).
> Possession of the disc
> A player establishes possession of a pass when:
> – they catch a pass and then they maintain that catch for more than one noticeable instant, and
> – they maintain the catch throughout all ground contact related to the catch, or until they throw the disc
> (…)
In WFDF rules, I believe the discussion would resolve around whether the defender in this clip lost the disc because of a ground contact (in which case he never established possession and it’s not a turn), or whether he fumbled it after establishing possession.
In any case, it seems to be that it’s already well covered by existing rules.