Ah, I must have always had Verizon phones that weren't capable of it, then.
There weren't many and all I know of were flagships. (LG G, Galaxy S)
Regarding the info menu, I just checked it. There's a switch for "VoLTE Provisioned" which is in the on position.
I'm at a loss then. I thought it was working on the G5+. Someone else may know more than I do.