Is my boyfriend a bad pet owner?

So my boyfriend has this cat named Simon. He got Simon around a couple of weeks old and he’s had him ever since. Simon is about two years old now and is mostly an outside cat. He’s extremely anxious and skittish around people. Doesn’t like sudden movements, and he has been like this since a kitten. He says Simon is more relaxed when he is outside, so he leaves his window open for his cat to come and go as he pleases.

He feels bad for his cat that he’s so anxious inside that he lets him out, but I feel like this is a lack of training and socialization and hes not really helping the issue by continuously letting him live outside. When his cat is inside he just hides under the bed but he’ll come out if he warms up to the environment and the people in it. Kids and noise aren’t his thing at all though.

One of the last times his cat went out he came back with fleas, and then those fleas in turn got all the way over to my house, as I live apart from him, and now my INSIDE cats are suffering with fleas.

All cats have been treated but this could’ve been avoided if he stopped letting his cat stay outside for days on end, let him socialize properly, and find ways to make him comfortable inside?

What do you guys think?