25D Upgrade issue in Redwood Page of Change Salary for Admins

We are noticing an issue where the end date is editable for admins in My Workforce—>Change Salary page. The changes has happened due to change in default setting. This is not part of 25D upgrade readiness document so this a bug in product?

We tried to make this field as Read-only however its displaying as null instead of 12/31/4712 as in 25C. This creates a bad users experience as the field is being read differently in each upgrade.

Is it expected that the default settings will change with every upgrade? If yes, does this mean that we need to validate every business rule during each upgrade cycle?