> At the very least it's unintentionally disrespectful

There is ZERO CHANCE they have used ai unintentionally

> also doesn't care enough to burn bridges and insult you.

By actively using ai they are stating that you are so much beyond them that even a personal "eff you" is not worth the time. One would have to actively try and poke some personally hurtful areas to come off more insulting than use of ai.