I think some people (including me) was expecting the damn first date that DPC has been postponing for so long. That could have balanced the tone of the character in this update. We could have seen "Romantic Sage" in the date, and "Party Sage" in the party. We have mostly seen "Party Sage" this episode (although there are a couple of cute moments) and it's bit of a disappointment because people was expecting a bit more of relationship development in this chapter. It's more a problem of this chapter being only a party and not having a lot of character's development or plot development.
But Sage behaves in this party like she did in the HOTs' party, it's not a character's recession. In the HOTs party, she fucks MC in the garden! She's even more sluttish there, so it's not a surprise. For some reason, she has been dating with a impotent gay for at least two years. Of course she's oversexed and wants to make up for the time lost with MC and in parties, specially the last Halloween party for her.
But, I suppose that we'll see "Romantic Sage" the next update. If DPC makes that in that date Sage behaves like a nympho slut too, only caring about sex, that indeed would be a character recession and would ruin her for sure.