Yes. For example, if I only use Relay-1 and you only use Relay-2, we'll never see each other. But if someone else adds both Relay-1 and Relay-2, then they would see both of our notes.

It's how the protocol is censorship resistant too. If Relay-1 bans me, I can just start sending my notes to Relay-2 and all of my followers can follow me to Relay 2 just by adding Relay-2 to their profile.