I assume the artist draws with the best of intentions in mind, so I wouldn't consider this bad anatomy. The pelvis is only partially observable, anyway, and even then it's only one part that doesn't (at least, IMO) marr the whole image.
Still though, if a flagger's going to complain about lines not being filled in perfectly on a sketch... Like, what even. A sketch's artistic value isn't based on how clean the lines and coloring are, it's what it depicts as a whole. Making those good would basically turn it into a finished artwork, for the love of Christ. See post #2641619.