That's the thing, people say that the two paths are different so the character acting different makes sense, devs included. But that isn't real, the characters are the same, the MC can stop them from doing certain things, and so be labeled as "alpha" or "beta", but the character would have always do the same thing if the MC doesn't interfere, so that makes them the same characters, with the same traits in both paths. Meaning that if a character like the mother, is a hell of a slut after a few days in the game in one path, she shouldn't be a prude in the other path, eiter a slut or a prude, either slow content with her or accelerate content in the alpha route, she is a huge slut, so she shouldn't mind much that the MC is her son, besides officially they are "steps", so I don't see why the content with the mom is that lacking in the alpha.For the beta/alpha route stuff, logically speaking, MC being beta or alpha shouldn't impact how mom/sis act. They should, in theory, be the same person regardless of how MC acts. Thus, for the sake of consistent personalities, the beta route should develop a lot slower to match the alpha pace, or the other way around.
Now, also logically speaking, mom/sis shouldn't view MC as a LI, he is their family member. So it makes sense for the alpha route to be slower, but not significantly slower, just to keep the routes comparable in terms of content.
The sister being a shy virgin/prude in the alpha while in the beta in one update goes from "first, dinner and then we will go slow, to fuck like rabbits" is called character inconsistency. Not only is an inconsistency between paths, but inside the beta path too, going from shy/prudent to fuck all because black dick in just one update. So since the characters are the same the moment we set a date in the "alpha" path with the sister, we will be fucking like rabbits in the next update and same with the mother, to not have a cahracter inconsistency you would say? Wrong, take a look at the dates mom had in the beta and now in the alpha, in one she is fucking like a pro and in the other just looking at a morning wood, wow progress, now we only have to wait another 385 updates before she do something.
Since this is an incest game, or a game that has incest in it, the family member should have some kind of affection to the MC at the start, to see him as a LI, since you know they are adults and weren't living in the void, they should have affection and if something would happen in the future, they should at least see the MC as a man from the start, they logically won't start seeing you as a potential match just because you become an alpha, that's dumb as fuck. But well even if we omit that, there have been already 21 in game days, even if they didn't felt something for the MC at the beginning, the devs had enought time to make something happen in a believable way, but nah, better do a full NTR path with them, because that's what people playing a game with incest want, to see the family members fucked by others instead of the MC, that will sure satisfy the incest kink lovers. And for the alpha lover, let's throw them another side character, that way they won't complain...