Bait and switch from the first chapter for sure, but i don't think it'd be bad to reintroduce a little lewd this long after. Honestly it'd make it more realistic since a person isn't a lewd horndog all the time, and usually you'd get just glimpses behind the curtain like this, so to speak.
I just went and reread the first one, and when he discovers her he says "She's doing it agaaaaaain" so she had a history of wanking it in the cafe before that. I forgot about that...it makes it even worse that we haven't seen event a hint of lewd activity since