It’s possible it’s a bug that’s triggered by your difficulty settings.
We have default difficulty on our server and while testing our purge base configurations I’ve solo’d 30-40 Lvl 1 purges and have not gotten any named dancers or bearers at Lvl 1. Mind you, we get them from higher level purges but not from Lvl 1’s.
This seems to indicate that either it is RNG (which may or may not be likely depending on how many Lvl 1 purges you’ve done) or it mean that it’s a bug triggered by your difficulty settings.