I think as long as something like the colour is different then it's OK. It would only be an issue if someone had 10 listings for say 10m x 1" pink ribbon and each ad was identical. As in, the colour, the length, the quantity were all the same. Someone could be selling envelopes and one ad could be in a pack of 5, another a pack of 10, another a pack of 20. Even though they are all exactly the same size envelopes, the quantities are different.

Yes, it would make sense for that seller to have a multivariation listing if the colour is the only difference, but maybe by having them all individual, it gives them more exposure in the search results?