Can iPhones send out messages months later on accident? Recipient has the number blocked, had shared notes

So I found a message on my bfs Mac that he sent to his ex girlfriend (who has him blocked). He said he sent it months ago and doesn’t know why it looked like it was sent the other day. The message was blue on the Mac but green in his phone. He said he was messing with a shared note he had with her and that might have done something to send it. There was also another message from weeks before that was blue but resent green while we were talking about it. I think he just deleted the old message and resent it to make it look like it just resent on its own. Could doing something with the notes or anything else cause this to happen? Has this happened to anyone else? Or is he just lying?