A long time since I was a Research Associate at a UK university (salaried short term contract) and trying to finish a PhD and I remember someone from outside of academia describing me as "hyper cynical" - that was after 5 years or so.
I left, co-founded a startup and never regretted leaving academia.
Edit: That comment didn't make me leave but it does rather reflect my state of mind at the time - which was pretty bitter....
If you're in a teaching position and students' evaluation depends on you remember that you won't see all that much genuine interactions, as many will try to appear at their best
I don't know where the person is studying, but it's not a general phenomenon.
I have still students around me, and the number of years don't seem to make them more or less bitters.