Thank you for this deploy on 4/14/2021. We, like others, have been using JavaScript to disable this functionality and also used the temporary "New Course Availability UI" feature option that will be going away since it was a temporary stop-gap.
While removing the deploy notes I do see...
Note: Currently this setting only applies to course dates and does not apply to section dates.
Was that note made because the ability to edit sections (and their dates) is a permission?

Continuing along the lines or permissions, to me it would seem more appropriate (and consistent) for there to be a group of permissions for managing course settings. One of those permissions could be the ability to adjust course availability (and dates). For this specific situation, doing it as an account setting seems to not be the best of interest depending on plans for future development as new features/options/ect are released but may need to be either enabled or disabled based on a customer's needs.
For example, one teacher-based role might have this specific permission enabled (allowed to adjust course availability and dates) and another teacher-based role would have the permission disabled (not allowed to adjust course availability and dates).
Doing an all-or-none account setting might not be the best path.
Just a thought for consistency, more flexibility, and looking towards the future.