A true random source of 65536**2 range values can (and will) spit out a (42, 42, ...) sequence out just as equally likely as (0x7b03aa9f, 0x33bcf51c, ...). If your argument is that it's less likely for same sub-ranges to be part of a combined range, that is correct, but the sum of probabilities for all these cases is in the below 0.00000...01% of the entire count of possibilities - as demonstrated by your huge generated files. So, a lot of convoluted work to exclude a (relatively few) close to zero edge-cases.