I actually read "all other post on the network" related to a specific user, not with a general meaning. Yes, it's not possible to automatically search/access any note, since there is no really a "global" feed. You have to query specific relays.

I don't see any problem with that, it's like the internet has worked since his inception. It is the centralized services that have accustomed us to this mode in recent times, at the expense of course of everything else, so Nostr exists.

Probably there will born search relays (NIP-50) that will offer this service, trying to aggregate/index as much relays as possibile. Ehi nostr:npub1xsgymm0ne3vndqpvsvy285qfpu59049t5n5twg9vetmt92cyn95snyzazx, are you listening? :)