It is said that several light coats are better than one heavy one, that’s why I prefer a smaller paint cup. It is a mechanical govenor to slow me down and keep the urge to apply the paint too thick.
In the case of having a large subject to paint that requires a lot of paint to cover, mix up the paint separately and add more to the AB cup as needed. Also, there will be times when the AB begins to get dirty and clog. I is easier/better to remove/waste a small quantity from the cup as to opposed to a lot.
The 100LG is an excellent brush, and the cup size is barely a factor in how you use the brush. After all, it’s only a 1/3 of an ounce! I also have a 150 siphon feed, and I find that makes more of a difference with a bottle attached, than the big cup on the 100LG.
A 1/32 A/C will require you to top up the 100LG as well. They are BIG. As Gerald says, the small cup size means you won’t be loading up too much paint.