I think the actual carry setup of folks, and the extent to which that is different from their IDPA gear, may depend on the region. In some regions, I could see that the full-size gun, vest, and hip holster thing is pretty solid. However, there are other regions where a gust of wind is enough to turn that setup into a revoked license, and talking about shooting is bound to get you dirty looks from 90% of the people you run into day-to-day. It's these latter regions that I'm more familiar with, which may partially explain why my experience is more in line with what you're getting at here.
Separately, I found the IDPA HQ email pretty sincere and insightful. I found this part interesting:
If by "CCP sized firearm" they mean ~G19 and "SSP firearm" they mean G34, that's a much bigger gap than I was expecting. In which case, I think CCP will be a quite useful class with regards to the data it produces, both in times and in watching highly-skilled shooters work.But after having some DM and MA level shooters shoot the Classifier with an SSP firearm and again with a CCP sized firearm, that helped to change our minds. It was discovered that the CCP Classifier times ranged from 7% to 24% slower than SSP times with the same shooter on the same day. This is a bigger difference than SSP to CDP firearms and is roughly on par with the SSP to Revolver difference in Classifier times. The compact firearms are harder to shoot quickly and accurately than some originally thought. This is probably why they are rarely represented in sanctioned matches, up to now.