It's a bit confusing, but as I understand it, FV3 refers to a trial version of the model. So every time they're working on an upgrade, they'll release both the old and new versions at the same time and eventually make FV3 operational.
What I assume is being discussed is the WRF FV3 that shows on pivotal weather. I believe this is a trial version (hence FV3) of a high resolution GFS model