It sounds like it's not digging down that is upsetting the pool contractor. It's moving the dirt to the lower level to make a base for the pool. All fill dirt must be compacted, but it's a good season of rain that really settles the soil. There is no way to say that 6 months, a year, three ? will be long enough to guarantee your soil's stability. The only way to know is to hire a structural engineer to assess your soil and the quality of the compaction.

A gallon of water weighs around 8.34 lbs. A 24' round pool holds about 15,000 gallons, which weighs over 125,000 lbs. The pool contractor does not want to be held responsible for something out of his control. If the pool collapses people will be blaming him first. He may be trying to sell you more than you want, or he may be protecting his business' reputation.

It does not matter if it's a steel wall vinyl pool or a gunite pool, both structures must sit on virgin soil.

If the present grade represents the proposed depth of the pool, at that point it must be excavated down to soil, than it can support either pool. Which means stripping any top soil.

Raising the grade just creates a wider gap to the virgin soil.

A soil engineer will be able to determine the type of soil and whether it's suitable to support a structure. Soil compaction is only good if that soil is suitable to compact and support. In other words, if the spoils material is full of sticks and twigs and top soil, it will never compact properly.

It must be removed and sometimes engineered fill must be brought in.

You must determine at what finished height you would want the pool based on your present grade. A good start is to hire an experienced pool designer or a landscape architect. The grade change has to be taken into consideration when designing. A structural engineer is a must also.

I have been on several new home construction sites whereas I came in after the spoils from the foundation were pushed off around the home perimeter. We would have to excavate down to the original soil to determine our finished grades.Many times this would change the entire pool plan and add additional costs.

Right now you have the advantage to check your existing grade's soil composition and move forward from there.