"All of the sudden it became G-Sync compatible."
I've been using this monitor since August. It's been great so far. Amazing picture quality in games, and great framerates with the 144hz. Also looks solid on videos and internet browsing. I could write a longer review about all that, but that isn't the point of this review.
A couple of days ago (Mid January 2019) I got a graphics card update for my Nvidia gtx 1080. After the update a notification popped up that my monitor was G-Sync compatible and that I could activate it in Nvidia control panel. Sure enough it was now G-Sync compatible and even indicated in game that G-Sync was activated when I had the indicator toggled on. So this monitor is advertised as Free sync/Adaptive sync, but apparently also is now magically G-Sync compatible as well. They should probably change their product title.