Nostr is not P2P so technically the relays could track the amount of traffic, and if they collect the ip-addresses I guess they could track who is communicating with who.
From what I understand Holesail needs the servers/relays only in the initial setup of the communication channel. That’s kind of overhead if all you want to do is one or two http api calls and disconnect (like when you pay a static lnurlp).
nostr:npub1h5t3asu90f2x48rxtcqkjvwhza7m6kngs7vjyanx8xqyswc6es2s4645z5 Do I understand correctly?