jscozz,
Crushed stone under a pool is used when there is a high water table or the potential of a high water table.
It is also used to mitigate the movement when expansive soil is encountered.
Soil varies all over the country. I can go from highly expansive soil to sand within a few miles. Same thing with high ground water table.
PB's need to know their building area.

I have very sandy soil... and high water table... I have had tests that show seasonal high water table level to be about a foot or so above the bottom of the pool. It is pretty dry right now, so I don't anticipate encountering water during the dig, but during a wet year I am quite sure the water table will be above the bottom of the pool shell.

Is the sub base compacted or just spread in the bottom of the excavation? Does high water table conditions affect the thickness of the gunite? My quote calls for 6" walls/floor.

jscozz,
The stone is usually not compacted. You should have a hydrostatic tube and valve installed. PB should be familiar with this. Most times no additional structure is required above normal. Amount of stone may vary. I would stone at a minimum the deep end that you know could be in contact with ground water. Usually 6 to 12" of stone. I like to use crushed stone 1"-, it's easy to handle and compacts well. Good luck.

Here in Florida I'm told its mandatory so they put the stone down . We just had the Gunite done yesterday.