It wasn't an extensive session, and "making up rules" is a bit perhaps strong as an expression. Perhaps "ignoring rules", would be more apt. It just replied with something that a DM might say in a given scenario, without understanding why.

Like it kept asking me what to do after I told it, in specific terms, that I use my action and my bonus action. Basically allowed me to sit there as a sorcerer spamming endless spells, didn't really understand spell slots or actions, but if you reminded it about them, then it pretended it had understood them all the time.

I'm sure it's somewhere in my history, but also, just go ask one to DM you an impromptu battle and check for yourself.