I have emailed the manufacturer with some questions about plastic boxes and MC cable, I hope for an answer in the next couple of days.
While visiting the website, I came across this information. It is from Carlon's website.
"
The SuperBlue Boxes I am using are just about 3.5". Is this too big for a
2X4 wall stud and only used for 2X6 walls? I am tempted to not use the
entrance/exit knockouts in the back and just drill some holes nearer the
center of the stud but it would take too much time.
It is acceptable for the NM Cable to enter the outlet box through its knockouts even though it comes close to the drywall. The NEC is concerned with damage to the cable from nails or screws. Outlet boxes are usually located low to the floor or above counter spaces. Also switches will be found near door opens and a little above the waist. It is unlikely that a picture would be hung in these areas.
Section 300.4(B)(2) does state that "if" it is likely that a screw or nail would penetrate the cable than a steel plate needs to be used.
Finally, if you drilled a hole in the box than you would void the listing of the product and would get tagged by the inspector.
(I highlighted and changed the italics and size of the font)
Last year we sold over 500 million boxes with knockouts without a problem pertaining to the NM Cable entering the knockouts."