This isn't something I would ever use because my optics are well corrected - but for people with unflattened RC's or ACF, or wide refractors, this would be a real need and it does correspond to the recommended way to focus a system with a curved field - and that is to focus a bit off from center so the overall field is an optimal compromise.
And even for people with such optics - they wouldn't always want to do that because they might have a small galaxy in the center and they want it as sharp as possible.
So I would say this does represent a real need for a small fraction of people.
An alternate way to achieve the same effect would be to allow a fixed offset to be added after focus. So you would still find focus the same way using all the stars - but a bump would be added to the final value - and it's up to the user to determine what that bump is.
I'm not saying what priority any of this is - and I wouldn't use it myself - but something like this would be important for a subset of users, and it is a recommended way to get best focus with a curved field.
Frank