exactly this! The test shows that there is a **very** significant difference on X/Y Axis.
I own a Hien for around 2 months now and can confirm that this is very clearly noticeable when you pay attention to it.
On the other hands I never notice this in games and still occasionally use other pads (as I'm not always at the same computer and only have 1 Hien pad) and it's no issues whatsoever for me and I never notice the difference of X/Y.
Pad is absolutely amazing, best one I've tried yet - perfect amount of speed for my taste/needs. Other than that the surface is kinda rough, I can see why some people don't like it for that reason but personally I'm not bothered by it at all even though I slide my wrist over it a lot.