strfry is already a cache, so a caching relay doesn’t make that much sense other than for adding proprietary features not available to the rest of the network. They could have just spec’d a lot of these features (note/zap stats, advanced search) as a nip so they would be compatible with other clients, but they don’t because they want to build a silo and break interoperability to create a facade of being better. They don’t have to play on an even playing field because they aren’t building a nostr client.