His versions also generally look worse than the original.
IMO it can only be considered a feature if Roy Lichtenstein ever demonstrated that he actually could draw correct perspective if he wanted to.
Art doesn't operate through skepticism, through doubting the artist's ability. It is about valuing what is in front of you, whatever it expresses or evokes. Nobody with any sense cares whether Lichtenstein could pass a Perspective Drawing Test.
It's why Roy Lichtenstein isn't Picasso.