and it would stay on for a bit as the capacitors drained?

Yeah, I’ve had that too, but I don’t think that that’s likely what’s going on there, if they fully shut the thing down, flipped the PSU switch off, and then started filming the card being inserted. LIke, it was maybe a couple of seconds at most. And honestly, I’d probably still want to avoid plugging stuff into a board while that is on, since I don’t know what other stuff also might be powered up on the motherboard. :-/