If a field is removed, it will not be included in exports by default. You can ask for all fields that were ever referenced in previous Form versions when you export data. Renaming a field is the same as removing a field and then adding a new one.
More at https://docs.getodk.org/central-forms/#updating-forms-to-a-new-version
ODK Central 2023.1 throws up a warning about this when you update the form so users know what to expect.