I don't consider 2x1/1 to be a substitute for a proper 3/2 rest moment.
I don't like the idea of having very long stretches without any break longer than 1/1 (since as Genjuro mentioned, 1/1 is one of the main snappings in muzu so it doesn't really feel like rest).
The way I personally handle it: If a section doesn't support a 3/2 rest, two consecutive 1/1 could be used to stretch it longer (maybe 32/1 or so) without a rest moment. But after that point, the mapper needs a true rest moment of 3/2 or longer. And if 3/2 still doesn't fit, there's nothing wrong with using 2/1.
Regarding whether a change is necessary:
It's not necessary, but it might be helpful. Raiden brings up a good point about having some room for interpretation in the RC. But I think a slightly more detailed guideline could be helpful for new mappers to give some idea of what "using rest moments less frequently is acceptable" actually means.
I don't like the idea of having very long stretches without any break longer than 1/1 (since as Genjuro mentioned, 1/1 is one of the main snappings in muzu so it doesn't really feel like rest).
The way I personally handle it: If a section doesn't support a 3/2 rest, two consecutive 1/1 could be used to stretch it longer (maybe 32/1 or so) without a rest moment. But after that point, the mapper needs a true rest moment of 3/2 or longer. And if 3/2 still doesn't fit, there's nothing wrong with using 2/1.
Regarding whether a change is necessary:
It's not necessary, but it might be helpful. Raiden brings up a good point about having some room for interpretation in the RC. But I think a slightly more detailed guideline could be helpful for new mappers to give some idea of what "using rest moments less frequently is acceptable" actually means.