I think it's more about the fact that there are all these nudist scenes, and the MC has actually finished having sex, what, twice (Allana and Olivia)? Including actual penetration of multiple girls without getting to actually finish. That's kinda literal blue-balling.
On that matter, everything with Lena has been pretty poorly presented this way, too. From dialogue, we know she's a virgin, but then the art studio scene blue-balls the MC while also forcing him to take her virginity (but that's not mentioned by anyone involved), and then following that up by having their first full sex be a mentioned memory, not an actual scene showing even the slightest hint of romanticism or affection... Really was a dick move.
For that matter, having the MC's first penetrations of several girls be not particularly sexy experiences sours things with those girls; for a lot of these events, where they're optional or you pick between girls, you're not even tracking variables so there can't be any later reaction to them (the choice of Lyra, Nori, or Valerie at the end is the big one here -- this is the first time having the MC's dick inside any of these girls, and Lyra hates it, but you're not tracking variables so the one you chose literally CAN'T react about it later on, because you made sure the game will never know which of those three the player picked, if any of them).