This and Party are related in name only. While this game is extremely similar and the code is at least similar enough to allow transferring player created things like characters in one direction to Sunshine, they are not the same game, in fact, that last part is a very big sign that they are not the same as the same game could use the cards without having to make changes that would make it impossible to use the cards transferred to it in the original again.
That said, both games supposedly have this NPC initiated dialogue.
I have four girls in an active sexual relationship and dating with full affection, none approach me and start a conversation. I do believe they can, it would make very little sense to keep something that basic out of a sequel to a game that did have that function, I may be having an issue with a mod that is installed and active by default that prevents it and that may be why they haven't started a conversation.
I'll check the mod options to see what might be going on there next time I load Sunshine, thanks for the tip. I wasn't even aware there were mods with that bit of functionality and now I wonder what the use of that function even is.