I think the limitation to 33 bits is because this is the smallest power of 2 which is higher than the world's population: 2^32 = 4.29 billions, 2^33 = 8.58 bi

I think the limitation to 33 bits is because this is the smallest power of 2 which is higher than the world's population: 2^32 = 4.29 billions, 2^33 = 8.58 billions, 2^34 = 17 billions,