Well, laptop g-sync isn't the same implementation as desktop g-sync, so I'm not too familiar with the technical details, the lack of a g-sync module does limit some of the engineering options though. Do you know the minimum refresh rate of the monitor?
It's possible the VRR window is too small for frame doubling, and your instantaneous framerate is dropping below the VRR window. Or it may just be some of the new frames are finishing during the re-scan, so they're delayed a bit. In any case, a 75hz max refresh rate puts some significant restrictions on any VRR implementation. The best option is an in-game framerate cap to keep you inside the VRR window, while reducing settings to maintain that framerate. It's still a lot better than a fixed refresh monitor, where you don't have an option that eliminates all 3 of judder, tearing, and input lag.