I always thought it was hilarious when it was said there was never a plan for the Eric/Lisa Sex Ed to be visible in the original BB, especially when there is literally a counter that checks how many times it has happened, which is what you would need to see different bits of the training each week. But to be fair it would be rough to have Lisa's sex ed start with Eric and then say you stop it at I dunno, a blowjob, then have to do all of the grind to get Lisa willing to suck cock when she was already used to it? It would allow for a possibility that Lisa could be more sexually experiened than Max. I think that, more than anything else was why it was dropped.
But the original game, after 0.6 or so made absolutely certain that tbere were certain lines that could not be crossed by Eric even if it made no sense in the context of the game. I loved the denials that Alice fucked Eric in the worst case scenarios. She would fucking blow the MC when drunk even if she hated him, and she LIKED Eric.
Not my favorite routes in the old game at all, but I think it was frustrating because they were intended and the hooks for them were still there, but there was no follow-through. But again, the ability to mix both an Eric route, and an MC route becomes difficult.