Got it, so then the relays would only serve up kind 3 requests that actually contain your npub, so your client doesn't have to look at every single kind 3 in existence each time it checks for follower updates, but it's still a massive amount of data to have to download every time it checks for updates, and that would need to be stored locally to avoid double-counting.

Yeah, not something that is realistic on a mobile client without a server that can do it off-device.