That doesn’t really make sense to me, because it would restrict you to exactly 16 CCs which are in sync. IMHO the groups are like pages, but all 16x16 entries react to feedback. On one group you have, for example, volumes of 16 channels, on the next group you have a specific fx send for 16 channels. Switching groups would become a hassle when the CCs won’t stay sync.
Sorrily the manual is not really clear about this topic.