I would characterize it more as "All models are wrong, some are useful, but it is never useful to use a model in a domain it is known to be wrong in".
We are extremely confident in the wrongness of relativity and QM in this matter, so using them in that particular way for philosophy is really a waste of time.
One could sensibly write philosophy of the form "If string theory is true, then..." or "If Loop Quantum Gravity is true, then...", because while those are not proved, they are also not proved actively wrong in the relevant ways.
Yeah, this is the fundamental tension in modern physics: are best theories are not consistent with each other (so we know they’re wrong or partial) and every experiment we do to test them confirms them to within measurement error.
It’s exactly the sort of situation that precedes a paradigm shift and it’s very hard to predict exactly what will trigger one.
We are extremely confident in the wrongness of relativity and QM in this matter, so using them in that particular way for philosophy is really a waste of time.
One could sensibly write philosophy of the form "If string theory is true, then..." or "If Loop Quantum Gravity is true, then...", because while those are not proved, they are also not proved actively wrong in the relevant ways.