That's certainly true. Not only could the painting of reddish lips and rosy cheeks be traditional, it is also a technique that an artist could develop independently. There are different ways of painting faces and there are many that were left unpainted. The thing about the VMs is that the artist was very thorough about getting those little dabs of red paint on nearly every face.
Another thing is that the presence of red lips is not simply a single factor investigation, but a dual factor authentication. Both red lips and cloud bands. It's like: "How many cardinals had red hats?" versus " How many cardinals had red hats and were armed, bendy argent et azure?" or anything vaguely similar? When identifying factors are very specific, it is good for them to be largely coincident, but when the identifying factors are more general, it is better when they are only minimally coincident.
Having both red lips and scallop-shell cloud bands in the same text, not to mention the same illustration shows that both elements were familiar to the creating artist(s) at a certain time and place. When it seems to be somewhat proximal to VMs origins, all the better to have something confirming rather than nothing to show.
Another thing is that the presence of red lips is not simply a single factor investigation, but a dual factor authentication. Both red lips and cloud bands. It's like: "How many cardinals had red hats?" versus " How many cardinals had red hats and were armed, bendy argent et azure?" or anything vaguely similar? When identifying factors are very specific, it is good for them to be largely coincident, but when the identifying factors are more general, it is better when they are only minimally coincident.
Having both red lips and scallop-shell cloud bands in the same text, not to mention the same illustration shows that both elements were familiar to the creating artist(s) at a certain time and place. When it seems to be somewhat proximal to VMs origins, all the better to have something confirming rather than nothing to show.