I think Nostr clients will build search using nip-94, so the gifs don’t need to be stored on nostr.build. nostr:npub1hee433872q2gen90cqh2ypwcq9z7y5ugn23etrd2l2rrwpruss8qwmrsv6 is just backing them up there while also creating nip-94 events.
Clients could build a gif search using tenor or giphy API by using a proxy which I think solves the privacy issue, but with nip-94 we’re not reliant on these APIs where the service can ban or rate limit you at any time.