Missing switch for iCloud Mail in iOS 26

On my iPhone running iOS 26, I have configured several additional iCloud accounts.

Now, under:

Settings → Apps → Mail → Mail Accounts → MyAccount@icloud.com → iCloud

the switch next to iCloud Mail to enable or disable it is missing.

The switches to enable or disable the three other possible options (iCloud Calendar, Contacts, and Reminders) are available. Only the one for iCloud Mail is missing. On iOS 18, the switch was available.

Is this a bug?