Usyk seems to confirm that he is going to fight on after Dubois

I agree, if necessary they could negotiate a 2026 fight, if he needs a long rest. It's then up to Parker's team if they want to negotiate room for a tune-up stay-busy fight in the meantime.
Usyk is keeping his options open, clearly. And getting stripped again only helps build up another 'unification' possibility for next year, but they don't want it too look like Usyk gave up the belt or avoided anyone, so asking for time due to injuries keeps everyone on all sides looking sweet.
It's all one big racket. Everyone cashes in this way.