They don't seem flat backed, and looks like 2 pairs per segment. Maybe juvenile? I hope these are a well know critter and someone recognized them. And I hope they are detritivores.
There really were a lot in a tiny pot, and ive made a small enclosure with the ferm they came in. Longest about 3mm, smallest sub mm. All white, translucent
Ah, they do loop a bit more... Longer, less clearly segmented (i.e. smooth, like typical millipedes compared to centipedes) than those. Also, i hope they aren't pests, but this plant did come from a biological plantery here, so i guess that does give some risks