Doppel points out Tio can't understand what it means to be flat since her own bust is 160cm, which is big enough to make Centorea seem flat by comparison.
For Kimihito this means that the only thing really stopping him from going all the way with his housemates is his uncertainty/not wanting to hurt them, and their own competitiveness with each other making it difficult for any of them to make a move. Albeit there are implications that the government has simply given up trying to enforce most such rules (especially with groups like Black Lily competing with them in the PR department), instead merely trying to make sure any actual sex takes place in private and that no one gets abused.