Just want to share some information in case someone does not already know. Hopefully it saves someone else difficulty.
These 6.0 TB hard drives have a shallower screw depth (at least on the bottom holes - which are used for mounting in my NAS).
When I called support (for another issue) I also asked about installing these drives, as the screws were rather tight - the agent advised me to tighten the screws - that it was simply because the drives are brand new.
As it turns out, the shallower screw mounting holes would not fit the lengths of the screws and because the screw was bottoming out, the screw holes were stripped.
Please - if you are getting these drives (and I would guess any model later than these) ensure that you are using shorter screws to mount them (not sure if the side holes have changed - check)
Now I have a multitude of these drives that are unable to be installed - thankfully, WD support will be replacing them after a lengthy discussion with them, but it still puts my NAS out of commission for at least a few weeks.