It is to some degree. Whereby your every use on the network is not data mined and used to build prediction profiles for selling ads, etc
Discussion
You can proove that no one is making use of the data we provide? Prediction profiles could very well exist from your notes.
Best to operate under the assumption your notes are being collected. Nothing to stop someone from having a relay to collect them and do with them what they wish, they could even disregard delete requests. What you post on Nostr is public for the most part.
It's also trivial to do. I ran a wot relay on a 2 core VPS with 2gb of RAM, collecting the notes from ~40k npubs. It barely broke a sweat doing that.
^ This ^
You don't even need to run a relay, you can just fetch from other relays continuously.
None of that matters as the ease of disposable keypairs is unlike anything in the normie world… hence why I built https://anonostr.com