i repeat: that the girls in the restaurant are having sex is certainly a fact. but BADIK has never for now given any proof of fact, so the players who are in love with those girls can continue to dream peacefully
but even what you point out are very vague clues. that 2 or 3 girls go to the bathroom together means that they prostitute themselves? then i have bad (or maybe good...) news for you all....
how can you say with certainty that this is not a flashback? it's at the beginning of the chapter like all the other flashbacks and has no obvious connection with what happens before or after in the story