As read the source it looks like that, data chunks of Default UVS Tables and Non-Default UVS Tables must be ordered the same as
s, but I did not see any requirements in the Spec restricting the order of data chunks.
If the data chunks are not ordered, OTS would report an error, triggered by line 531 in cmap.cc (https://github.com/khaledhosny/ots/blob/master/src/cmap.cc#L531
). The code forces that, the UVS data chunk referenced by the last varSelector must end at the end of the entire CMAP subtable.