Is it possible that the the buffers are all on 256-byte boundaries because the program is using DPTR to access memory and they only want to deal with updating DPL as opposed to maybe having to update DPH as well? Another possibility here is that the programmer (the compiler?) uses @Ri with the MSB fixed in P2.

I have, on a TEMPORARY basis, ocasionally located buffers in fixed addresses during the debugging phase. When you have REAL problems, it is sometimes convenient not to look up where a buffer is every darn time. Maybe the original coder did that and did not see the need to clean up.

Erik