When time tracking is switched off in Jira system settings, the time tracking fields are still available in Jira Plans. It is still possible to configure time tracking, even if it does not work. Users have the option of adding the "Estimates" field to the plan and filling it in. If you now want to review and commit the changes, you get a error message. However, this is because the field has been filled in, but time tracking is switched off. It's kind of nonsensical if time tracking is deactivated, but you still have the functions in Jira plans, but they can't work. This leads to confusion for users and should not be possible.

I have already opened a support ticket and received the answer that time tracking is a core functionality of plans and cannot be switched off.
In my opinion, however, if you deactivate time tracking in the system, the function should not be available in plans either.