Yeah, he's had a weird playing history, that's for sure. For instance, he played 5 Grand Slam main draw matches before his first ATP main draw match (which is still his last).
Winning a Challenger with only one Futures semi-final appearance is hardly run of the mill either.
The large draw means up to ranking 100 have direct entry to grandslams, and there is a large qualifying field as well. No ATP event can give direct entry to that number of players, so it must not be uncommon for players to be in grand slams before they can access ATP events.
Of course Nick Kyrgious is still outside direct entry to grand slams, but not that far outside. He has a long way to before gaining direct entry to ATP events though.