Bingo! They have nothing else to choose from. Some of these issues are also just inherent limitations of LCD technology as a whole, namely the strobe crosstalk issues and how blur reduction only works optimally in certain scenarios. Also it's a shame about those peak response times, because if you look at the other transitions, the Z35 at 200 Hz can be lightning fast (well under 4 ms).
But the 20-55 ms response times are just a by product of this AMVA panel. Look at how well the Philips BDM4065UC does in TFTCentral's review with regards to response times especially with no overdrive. It's 4k 60 Hz and faster than the Z35 at any refresh rate, and faster than the 120 Hz 1080p Eizo Foris FG2421. No 55 ms response time peak, only one 18 ms peak. This combined with how well high end SPVA TVs fare in response times have me convinced if someone tried they could make a 1440p 120-144 Hz VA panel with overdrive and very good response times all around.
Unfortunately nobody has reviewed the XZ350CU yet but I'm sure it will have the same issues as it has got to be the same panel, so the response time will be very similar.
The ghosting/blurring issue was fixed by reverting to the older Nvidia driver 358.91 reported by people using the unit.