I would agree that is Bryce's character but when one gets to that point, denial can kick in. Next year I'll be healthy, next year I'll bounce back, etc. Pretty hard to walk away from the money too. And if your decline is accompanied by injuries no reason to, either.
I'd settle for him just accepting a part-time/bench role if it came to it.
There's not going to be any drama. The Phillies are going to give Bryce his extension. The real issue here is whether they (and he) should even be so firmly committed to him playing here forever no matter what. What if the team does need to rebuild for a couple of years? What if he does no longer merit a starting job? Paradoxically, if I were the Phillies my one counter-negotiation would be to take away his no-trade clause after a certain point but the optics of that wouldn't work for anybody.