uhm, well most games like this just have the purple ren'py tag, from what I've seen, so I'd recommend doing that too.You may be right, but we're using the classic for vn scheme, where we have static images, sprites and a dialog box. If we don't write the vn tag, then which one will more accurately reflect the essence?
also, about the scheme, I get what you mean, but on this site it kinda means something else... I'm sure you can safely use the visual novel tag on steam, for example, but in here the "VN" tag is a lot more specific.
also also, that scheme also applies to RPGs and other types of games... it was born out of older game design limitations, so plenty of different types of games have used it... it's more a case of the first VNs also adopting it... but anyways, neither here or there =P