I don't have an answer, other than I have not heard of any issues between pages. For the most part, they all act the same.
Maybe it has something to do with caching?
You can see what happens when you try the mirror address of 0x2008xxxx which is 0x6008xxxx. (as in, use the CPU to write data to 0x6008xxxx, and then also set up the DMA up for 0x0x6008xxxx)