I'd like a bit more information about this. I can see three possible reasons for needing the new adaptor:
(1) The old one included with the ZCU102 was faulty in some way (eg. was only actually designed for USB2 despite having a USB3 plug). In this case any USB3-compliant off-the-shelf adaptor should work fine - no need to buy the WhizzSystems one, especially because its mechanical design makes it somewhat awkward to use.
(2) The original adaptor is fine but the ZCU102 requires some additional logic to meet USB3 specs. In this case, it would be nice to have the schematics for the ZCU102 updated ASAP to say that the USB3.0 design shown there is not valid. The Xilinx devkits do tend to get used as reference designs for a lot of boards, and designers would like to know that the current design is problematic.
(3) The original adaptor is fine, and the ZCU102 design is fine, but the Zynq UltraScale+ (even the production version, since this adaptor is needed for the production ZCU102) requires some additional logic to meet USB3 specs. If this is the case, Xilinx really needs to provide more information about the problem immediately - people are designing boards based on the Zynq UltraScale+ right now.