As an amateur artist myself, I've often fudged shadows and shading to emphasize or de-emphasize certain things. Often I'll make slight "token shadows" to at lea

As an amateur artist myself, I've often fudged shadows and shading to emphasize or de-emphasize certain things. Often I'll make slight "token shadows" to at least have enough to say "here it is" if somebody fastidious complains, but I'm still happy to downplay a shadow if it fits the intended narrative of the work. Those actually judging the art of the times probably didn't really know or care, as the illustrations were often done for social reasons at least as much as decorations. As the canon of "shadow science" increased, there would be more pressure to also please professionals who may judge your work and pass on the word. "Don't hire Bob, hire me, for he does shadows wrong. Here, I'll show you using candle light and these books...". Pleasing customers and pleasing artists are often different things. Bach pleased artists much more than "customers" and thus made a middle-of-the-road salary despite being a musical genius. Mozart was arguably the same way, as he had some trouble keeping up with short-term fads.