I mean I think you are right that the punk part of dance punk is maybe more from post punk, but I don't think I've ever heard LCD Soundsystem described without mentioning dance. I don't see how anyone would say that a genre that uses dance in its name isn't dance music though, right? EDM it is not obviously.
Talking Heads use a lot of african rhythms and afrobeat influence which certainly has its roots in dance, but I don't think most people would describe them as dance music like they would Blue Monday and forward New Order or LCD Soundsystem. I guess I wouldn't argue if someone said some of their stuff was dance rock though.
I'm not arguing that anything isn't post punk, but saying the absolute that LCDS isn't dance I think is a very hard position to defend. Tons of much less dancy post punk bands (including synths) as well, but even then, hard to argue something isn't dance when it is music. Maybe easier with some This Heat?