[vidarh]

I think it's more likely it "just" had more colours, and possibly used a different graphics mode for parts of the screen. Lemmings strikes me as a game where the size and number both precludes using sprites for all of them, and where moving the Lemmings themselves shouldn't be computationally costly enough to be a problem.

Though the Amiga does allow changing the positioning of the screen over a larger bitmap, so e.g. panning the levels without much/any copying might have been an option? Doesn't require the copper, though.