One of my starting colonists (female) had a synthread T-shirt and no other clothing. I tested by starting a bunch of never-saved new colonies, and almost all of the colonists had enough clothing, but I ran across 1 or 2 more with only pants or only a shirt.
Spawn pawn > Colonist in devmode sometimes makes colonists without enough clothing too, so it's easy to reproduce by spamming it and checking all the clothes (or just noticing the ones wearing no shirt or jacket).
Even if it isn't just "always T-shirt and pants" like it once was, I still expect starting colonists to have enough clothing not to be naked.
It's actually by design. They didn't manage to grab anything while escaping the ship.
Maybe they were in the middle of some sort of "joy" activity involving no clothes when the ship blew up.
lol.