Quite frankly it makes it feel like a scam.
All the people hyping how Nostr uses tamper-proof messages and is decentralized, censorship-resistant yadda yadda, recommend you use apps that don’t even check relays aren’t lying about authorship of messages.
About trusting the relay for sending or not it’s a bit more than that.
Relay might seem to accept your event but only forward it to some people, or delay it, etc. there are numerous less obvious forms of manipulation.