Do I think it is childish to have suggestive Adventurer Plates? Yes.
Should they be warned? Yes.
Should they be harshly banned (3-20 days)? No.
I don't think there is a good reason to be banning people for a suggestive adventurer plate that doesn't even show any nudity. Square Enix knows EXACTLY what they're doing when they added in subligars, swimwear, Coeurl briefs, 2B thighs and the like.
You cannot have your cake and eat it too. So many facets of this game are built to facilitate suggestive and 18+ activities. They know their thirsty audience and they want to monetize them. But the moment they go a bit public? That's a ban.
Slapping them with a 20-day ban is way too extreme for something that 99% of adults would not be offended by, minus an eye-roll. You get a lower ban duration for harassing someone in chat and using racial profanity.
Most of the suggestive poses so far are tamer than whatever music video Nicki Minaj or Cardi B made in the past ten years. This is such a disproportionate punishment for something most adults aren't bothered by.