Let's put it this way, sex education classes are a normal thing. It would also be possible for Sophia to teach her own son at school. In that respect I have no problem with the idea of sex education taking place privately between Sophia and Dylan. But a sexual escalation between the two just wouldn't be possible without the other events Sophia has experienced so far.
Only if you let the SexEd story stand on its own does it make no sense.
The last event with Sam should also be seen in this context.
Sophia has been subjected to constant sexual temptation and stimulation over the past few days. The fact that the event escalated to such an extent, Sophia masturbating while Sam sucks her breasts, would be totally unbelievable without the other events of the past few days.
Only embedded in the other events of the last few days can I follow L&P's thought that SexEd is the starting point for a sexual mother/son relationship (increasing horniness and moral degeneration of the MC).
From this starting point you can certainly tinker the cuckold route in which Dylan can take advantage of the fact that Sophia is becoming more and more of a sexual predator and loses all scruples.
But for a romantic route... it takes a lot more than that, and SexEd isn't a good place to start. And then, by definition, the romantic path is first and foremost a monogamous path. Especially since there's Liam, husband and father, and he's not an asshole like in many other games. Also, unlike Sam, Dylan isn't gifted with talent. How Dylan is supposed to emancipate himself from his father via the SexEd path, how it is supposed to become a real alternative for Sophia, I can't see.
Incidentally, this is also shown in many other games in which there is a mother/son relationship, which is completely unbelievable, even if the father is a total asshole or is dead.
