Is there any justification for this kind of "subsumption" mattering to anything except philosophers, and only for historical reasons?

If we establish a correspondence between physical actions and computation, then we can work in either regime and port it to the other, at least when conditions suit.

"Primes don't exist because physical matter can implement computations of primes and therefore they're indistinguishable from the actions of its physical implementation for which primes are a weakly emergent phenomenon and are eliminated as anything else" sounds like a perfectly awful way to try to understand anything.

Ontology is about reality but it is for us. We're the ones trying to understand. This just seems like a really unhelpful way to do it. Not only is it revealing nothing, it's actively hampering our ability to understand at every level.