If anything breaks at number like 33, it means that there was a restriction upto 32, why 32? 2^5.
It’s not trivial that most of the restrictions are in a factor of 2, MongoDB document size cannot be more than 16 MB, on a collection there could be maximum index, no more than 64. etc.
why it works as 32 and then next, because till 32 it can achieve in one operation and for last one it can see the next one as another operation. But it cannot go for 33 in one operation.
Most of these restrictions are basically sanity check though and not really technical boundary.
As for why it is almost always a factor of 2, I want someone else to answer or in other words I don’t know.