It's no different from sending an email to the wrong address. Disclaimers to the contrary, it isn't the responsibility of the recipient to ensure the address (phone number, in this case) is right.

There's no other metadata for text message recipient other than the phone number. You can't see that the sender fucked up before you actually read the text message.

Yes and my point wasn't about reading the message but about sharing it with others. If you think you're the intended recipient because the only information you have is the recipient's number, then that's one thing. If it's talking to Elon Musk in the message then it's clearly not addressed to you, so you don't have the same grounds for sharing it.

Well, legally speaking there's really no difference.

Yeah, we're not legally speaking.