Yeah, that's what we call a disorder now. As in, some "autistic" or "obsessive" traits can be fairly common at very low levels, but we start calling them disorders when they severely impact your life. Like being physically unable to stop washing your hands 200 times in a row to the point of making yourself bleed, that's a disorder - but being unable to step on black tiles or odd steps on stairs is not severely impacting your life. Same reasoning for things like gambling or porn, it's an addiction only when it starts ruining you, your work, or your family life.

Not sure how damaging that could get for a train or ship lover, you could probably find workarounds for the "forgetting to eat" thing. Like packing a snack. Depends if the person is holding out for weeks on ends while they have other obligations to other people.

I don't know that the mania phrasing is that significant for a serious armchair diagnosis like that. As long as someone constantly stops to watch a ship passing by like they're under a spell, they could call it a mania, inspired by some god or another ; making lists for no reason could be enough for people to call you bonkers (even in the last couple centuries, you could still send people to an asylum for the dumbest assumptions). We're certainly missing details, but that could go either way, it's not enough to suspect something big beyond "people used to think basic mental health was the voices of gods."

Yes, he's happy when they return, but that doesn't mean he's happy a majority of the time during these periods.

He's making lists. He happy.