The best way parallel universes were explained to me was, I think, in a Radiolab episode. Might have been NDT talking. Basically the idea was, as he explained it, that infinite means infinite, so there is going to be a universe with every possibility, and also (presumably) an infinite number of identical universes to ours. The idea that a new one splits off every time a different possibility happens is, I think, not based on science (though I'm no expert in that), even though it was in a Star Trek: TNG episode.
Anyway, yeah, it is based on theoretical physics, but it still doesn't feel real. Even less real is the idea that one can influence another or contact another in any way. Actually there's a lot about theoretical physics that simply doesn't make intuitive sense. I suppose people who grow up with SF stories based on those ideas might have an easier time with it.
The homosexual relationships thing, well, it is what it is. It just seems they're way overrepresented in fiction these days, and particularly in the stories here. (Of the romantic relationships in the EP stories I've listened to in the last couple of months, my perception is the ratio is nearly 50:50, which is way out of line with my experience of reality.) Maybe people are simply making an effort to achieve some perceived goal of making up for past underrepresentation. Or maybe they're just trying to seem extra-cool and progressive. Or using it as a gimmick.
Anyway, the reason I brought both of those up is they (the premise and the relationship) both felt like gimmicks in this story. But then again, isn't the typical SF story based on a gimmick? I don't know. Just thinking "out loud," as it were.