You're not too far from the truth 
Kitty, I'm not saying it is not possible, that just might be
their reason but I have never seen an LE unit (stateside) use a
revo for CQB. When you are entering a room, house, bldg, etc, you
wanna make sure you have as much ammo as yu can carry because you
never know what is around the corner. In Singapore, CQB might mean
facing a individual with a parang. In the US, CQB might mean
entering a house with a criminal behind a stolen AR15 (that's 30
rounds).
FYI, one of things we do during training is a tactical reload (swap
out a new magazine - where possible) before entering the next room,
after the first or last has been cleared. We do so becos' we do not
know what to expect and don't want any surprises like a slide lock
because there was only one round left.
I'm outside DC and I don't have one in every nook and cranny. I
have to be concern about my little one. I do carry one and my wife
(who's Asian) has 'skills' too. I like to say we have a few 'well
placed' firearms for home protection. Have you ever heard the
saying that a pistol is only good to buy time to get to a rifle? A
Remington 870 pump is our home defense tool.
I work in the industry, so to speak, which means that even during
some of my travels to the other states, I do check in my firearm at
the airport.
D, PM sent. I know the MP5 is still a hot ticket item in the
rest of the world. It just doesn't fly that well stateside. H&K
are trying to get rid of their stocks of refurbished units at well
below market prices and they are literally about 45 minutes away
from where I am. No matter what some of my associates here think
about the MP5 (everyone wants a shortie SBR or at least an M4), I
think the MP5 is still a very formidable weapon system.
DVC.