The more highly advanced the robot is, the greater the concern that it's sentient. So the more similar a sex robot (i.e. a robot whose purpose is to provide sex, and is not allowed to refuse) is to a human, the more similar it is to a sex slave as well, in practical terms. Nadeshiko is very easy to mistake for a bio-human, even if it's unclear if she's actually sentient.
This could be a reason for a legal ban of realistic sex robots, and a the reason why Tsuda may feel bad about leaving Nadeshiko in "sleep mode" longer than necessary. Powering off Nadeshiko any time she doesn't "need" her (e.g. for sex, or companionship) might feel like denying any semblance of individuality or agency from her, perceived or real.
An interesting interpretation that'd explain a lot. I'd like it to be explored more in the story, but I fear that this manga is much more interested in wacky hijinx than in questions of sentience and humans' relations with the AI...
Yeah, it'll be interesting to see how this handles things going forward. These first few chapters feel like setup for the overall premise, so now that that's out of the way, we'll have to see whether it gets into meatier topics like that or sticks to the current tone, and to what degree in either case. Personally, I feel like the shenanigans and serious explorations don't necessarily have to be mutually exclusive, so I hope it aims for both, but only time will tell.