FedEx Express has been doing DIM pricing for a long time.
Both Ups and Fedex ground started just this year dim'ing under 3 cubic feet if Dim Wgt is greater than actual Wgt. IMO if one carrier didn't do it, the other couldn't. This along with USPS reducing rates up to 40lbs, it will be interesting.
I agree, the long standing want was heavy/dense packages, now they are all more equal by dim'ing, so smaller boxes are probably more beneficial running the #'s now, since those won't wear and tear their labor force as much, that is if both can keep the volume.
Some are getting new dims greater than then standard 166, others are getting flat out waivers. I do find it funny that perhaps the biggest culprit Amazon, probably the biggest single reason to do this, will almost assuredly get a higher dim divisor or a flat out waiver. What this means is they continue to grow, since their price remains unchanged and their competition, smaller has to pay dims, so they pass the higher price along to their customers. See what just happened there?
USPS also play a role here with Amazon.
Interesting time.