"Someone and I" syntactic-analysis

This is a topic I became curious about, and I’m not able to find much info online about this if any. This being the grammatical rule of "Someone and I" where you place yourself last when listing yourself and others, versus the "I and someone," which I’ve always been taught is incorrect, but many people have been saying it is. I’ve looked online for the reason why it’s one or the other, but more often than not, I come across the "is it someone and I or someone and Me?" question which doesn’t help and is not what I’m looking for. As I mentioned, I am curious about this grammatical anomaly; Which is correct, and what is the reasoning/rule that specifies why it is correct?