Finally, because initially people didn't realize CustLem2 is intended, many people are less inclined to try again after finishing it on CustLemm.
I guess, but they could, you know,
read the title! Not that people should be expected to know the specific number of the max safe-fall distance (before the +3) of each version of Lemmings... But the non-CustLem2 version of beating the level isn't satisfying at all (you just kind of go..), I don't see why passing it that way would make people not want to play it the real way.
And about the not reviewing 2 or more times in a row, that has been ignored several times in a row for various reasons. If no one's reviewing it and especially if no one is really trying to pass a level anymore, then go ahead and review two.