I have gotten "Intuit codes" via text before when I did not create them, but assumed someone made a mistake in their phone number. However, I just got another and logged in to make sure I had not been hacked
That is all you really can do ... you cannot stop someone from making an error in the system.
Well if they entered the wrong phone number on their account they are not getting their codes or meaages. It won't affect your account.
I'm shown the option to log in to their account, so they did create one with my number. I've also been getting repeated confirmation codes since 2020, so I don't think it was a one time error.
Yes it could be just a one time error if they originally entered the wrong phone number the first time. It keeps using it to send them the codes. I wouldn't worry about it and ignore their messages to your phone. Watch for real messages about your account and tax return.