It's been what....2 years since ICE adopted the MPX? Still vaporware, they have yet to see them.
Sort of a low-profile tacit admission that the gun isn't ready for duty use, regardless of the rave reviews by civilian shooters.
"Better to let everyone think you're an idiot instead of open your mouth and remove all doubt" sort of situation on SIGs end, is my impression.
With that said the military SOF variant of the Rattler (LVAW) has been in use since 2014 and is still not terribly common to see overseas, regardless of the rave reviews by civilian shooters. That's a little telling to me as well.