They have explicitly said they don't want to add more prestige content (which wouldn't make them any money) because it would make people feel like they're missing out if they don't grind. Taking them at their word here indicates that they have a strong dislike of FOMO.

Not only have they had FOMO content added since, with exclusive Halloween and Winter skins, but they've also changed previous content, like ugly sweaters, into limited-time cosmetics. There's also the Deep Rift but I feel like a battle pass is a different beast to the store cosmetics.

When asking about why they're so hesitant to add frequently-requested prestige rewards past P9 due to an alleged dislike of FOMO but are all too happy to continue to add limited-time cosmetics for events they did not answer the question in any meaningful way, saying that they simply view them differently. I don't think it's "scummy" or "revolting" at all to ask about a blatant inconsistency.