By counting grid points it looks like codes in the form 0[1-9][32-99] are the least common with a few exceptions (like 0990 or 0987).
I suspect this is leading zero bias: a leading zero is not meaningful mathematically and we tend to drop it. The exceptions are dates. The day first block doesn't extend vertically into an unused area but the month first one drops off a cliff around 32 because no month has 32 days.
It was so frustrating when I was studying mathematics, I feel like just one more dimension would make understanding lots of concepts much easier; for me there is simply not enough points to extrapolate from: 0D is the degenerate case, 1D is trivial, so only two, 2D and 3D, are left to play with. %(
I suspect this is leading zero bias: a leading zero is not meaningful mathematically and we tend to drop it. The exceptions are dates. The day first block doesn't extend vertically into an unused area but the month first one drops off a cliff around 32 because no month has 32 days.