Anything is possible but I suspect the Primal team made the design decision to use a cache for their app so probably won’t change it. I think it could make sense to implement a fail back to local processing of notes directly from the relays in the case that the cache is unreadable. At least that way the app would keep functioning if there was a cache outage, although that would likely be with a more limited set of features than with the cache.

I could see it being a design decision since that probably simplifies a lot of client code and they're building several clients. But given that they're trying to make a profit somehow that seems like exactly the kind of thing you'd try to charge for.