The sad reality for YCG, and they bring it up in the article, is that all of these characters weren't particularly gendered one way or another. I never really got this stretch goal, it seemed (and it indeed is) like a lot of work for a barely noticeable difference. Black Knight looks like he's just wearing somewhat different armor. In sprite form the difference borders on non-existent for Shovel Knight and Black Knight.
Still props to YCG for doing this in the first place and going all the way about it.