x-key rollover is defined as the minimum number of keys it takes to lock up. In the M's case, it is 2. The position on the keyboard is largely irrelevant. Just because keyboard a will take all the numpad keys, but only 2 alpha's does NOT mean it has 9KRO, it has 2KRO
Having never used an M5-2, I can't say 100% it is 2KRO, but I suspect the matrix and controller are largely similar, if not virtually identical to an M.
Look, I love the M's, and BS in general, but you defend their known weaknesses too much. Just chill out, there are other keyboards out there, and they are better at some things. When you get to availability, value and longevity, then the M's are pretty much unassailable. However, you need to stop trying to pigeon-hole them into spaces they won't go. Although I do game on one, I am not a serious gamer, and I have spent literally years getting used to what the can and cannot do in a game. Race Driver:Grid is not a good game to play on keys, but you can scream around like a maniac in NFS:MW. UT99 is about the limit of FPS games, and I only own in that game on an M because I have been playing it on an M since it's launch, OVER 10 YEARS AGO!
tl;dr
The M's are good, but have limitations. Get over it.