Yes, it is true that in the XT-9, the 2x2 can only use the lower 5Ghz band (36-64) and the 4x4 can only use the mid-upper 5Ghz band (100-165).
However, here in the US, where I did the tests, the lower non-DFS channels (36-48), which the XT9 2x2 were using during test, are limited to the same...