FWIW, The UAE also has two units just like the ones that the USA has. One is listed as a Terminal Mode and the other is Forward-based, just like the USA. Both Forward-based have a range of 935 miles. Both Terminal mode have a range listed as 540 miles.
Given the same scenario, just swapping out units, all four detect the incoming DF-21Ds at a range between 244 and 267 miles. The units with the 935 range were no better than the 540 mile range.
When looking at the UAE, the unit that is listed as "Terminal" discusses the Forward-based version, which appears to indicate that, at a minimum, the description is wrong.
Not knowing lots about it, I would assume that the units with a 935 mile range would likely be able to detect the same units further away than the Terminal mode does. But, I don't know if this is the way that it is designed, or not.