Instead of Toggle button for SMS forwarding (iOS Settings app > Apps > Messages > SMS Forwarding) in iPhone ,a grayed out text appears if the other Apple device is logged in to iCloud after the primary iPhone.
Messages in iCloud are switched On for all devices, and all devices are on latest iOS, iPadOS, macOS. iMessage is also On.
The toggle button appears for SMS forwarding (iOS Settings app > Apps > Messages > SMS Forwarding) in iPhone against any device logged in to Apple account in the following conditions: 1.) the iPhone is restored as new and logged on to the iCloud ID, after the other Apple device was logged in to iCloud with same ID. In other words, the iPhone under consideration and its Messages in iCloud are logged on in the last out of all other Apple devices (iPad, macBook, any other iPhone); or
2.) the messages in iCloud is toggled "Off" in the respective other Apple device.
Perhaps the above condition (2) is emanating out of the Apple support article https://support.apple.com/en-in/102545, but the condition at (1) definitely does not seem to have any basis. The behaviour at (1) seems a bug.
