So I just wanted to revisit this since I had to upgrade to the 2019 unity version which still has this issue.
I noticed that it looks like the virtual screen position is relative to the chest/spine direction which can sometimes lag behind the position of the head due to the way the IK is implemented.
Is it perhaps possible to position the virtual screen relative to the head direction instead?
Viewing post in SUVA - StreamUrVirtualAvatar comments
Eyetracking is implement to always look at the camera, it is not relative to the head or chest. You can test this by looking at the center of the SUVA window and rotating the camera left and right, you will see that the avatar keeps looking at you until it hits its range limit. In SUVA 2.0 this entire system gets updated and you will be able to choose what is being looked at. SUVA 1.X will not receive any feature updates but only bug fixes when needed. This is not a bug though, this was by design.