When on the roof with Silverhand you select who you want to call to say goodbye, than that character is treated as romance, and the others are like nothing ever happened, even in the credits
The game is scandalously unfinished, to a level I've never seen before in AAA gaming. ME Andromeda was feature complete compared to this game.
Quoting your quote because there can never be enough emphasis on how royally fumbled River and Kerry's arcs were.
The romances barely acknowledge V after their missions are complete (River hanging up immediately and then never picking up again if you call comes to mind) I'm not totally surprised they don't acknowledge each other.