Correct as the 2000 video mode was 640x400. You need a VM1 or CM1 for the 2000.
I have a fairly nice CM-2. But the only reason I bought it was to have a period correct monitor for a 1200 / 1000. Though Tandy did push the CM-1 for the 1200 with the STB-400 hi-rez CGA card. My 1200 came with...