When I did the pooling for AW2018, I looked at the number of entrants from the previous years in those divisions. With the new divisions at AW2019 this year, they didn't have the luxury.
I will say this. Scheduling and pooling was probably the hardest thing to do and impossible to get right. There are so many factors from the obvious ones (previous year size, number of eligible players) to the not so obvious (well if I give this pool an extra 32 people, that means I have to reduce this other pool or that means they have to play course B now instead of course C).
There will always be that division that fills really quickly every year.