The friendship probably fractured slightly because, even though he seems morally bankrupt and completely lacking sympathy, Art would’ve liked Leo to trust/rely on him and also he may have been this || insulted by the idea that Leo thought she could hide it from him when he’s probably one of those bean counting mechanics that keeps track of every single metric. If they haven’t had a Come to Jesus moment already, then he’s probably polite but distant, whereas before he would’ve let her in on the weird shit he thinks about, like how hard would it be to replace his digestive system with some kind of nutrient pump so he doesn’t have to waste time eating. I keep coming back to the scene from the original Ghostbusters where Peter Venkman is like “This reminds me of the time you tried to drill a hole in your head” and Egon is like “It would’ve worked if you hadn’t stopped me.” Whichever one of them is Venkman or Egon changes depending on the context.
He probably teaches calculus and physics and other abstract, egghead subjects.