He's skirting around it with "something happened".He is very evasive with the actual details of how it started. As in who made the first move? Who initiated it? That's important I think considering the age/power gap.
This ain't the movies. There's no lingering stare followed by a sudden intense kiss. You were "mates" who worked together with a significant age gap, never mind MM either just becoming an adult or being 2 years into adulthood. Philth also knew MM as a kid. And it sounds like it may have happened at work. So not a drunken after hours social thing.
There's too much awkwardness and boundaries for it to have started with one of them making an unexpected move. Not impossible but unlikely.