Understood. It may be boiler plate for the accountant to reach out to do year end planning regardless of your individual situation. It also sounds like you have a good bead on your business status and requirements. Not all business owners do.

CPA here. As another poster said the work done prior to the end of year will allow prep of the final return to go more smoothly so it should not be "double" work or billing. I think it is a good strategy to look before the end of the year at the tax situation because some things may pop up that can only be mitigated prior to the end of the year. It will also save time in gathering info now rather than during the busier tax season.

Also, asking your accountant what the goal of doing a mock return is a reasonable question. Ideally, a good accountant will be a trusted advisor looking out for possible areas of ways to mitigate headaches for you.