There is another reason you might want to split a MEGX loop from stereo to mono. Say you split loop 1, loop 2 and loop 3 into mono loops. You'd now have loop 1, loop 7, loop 2, loop 8, loop 3 and loop 9. All six loops would be mono.
You could use loops 1, 2, 3, 7, and 8 for pedals placed in...