That does sound like a setting is bugged somewhere, or perhaps like one of the problematic settings is not toned down on the low preset. It's hard to tell without testing on the specific hardware. I'm curious enough that I may install it in more devices with less VRAM and mess with the settings just to see what happens.
I do think if they hadn't told people that performance was going to be messed up you'd absolutely assume that's a bug, given that, as you say, it doesn't match their spec notifications.