Always On display

I'm updating a timer app that is written in regular Swift. After being built using watchOS 8 the display stays on (Hooray!) but none of the text elements update (Boo!).

I've read the documentation at: https://developer.apple.com/documentation/swiftui/text

But this suggests that the only way to get the Always On display to update is to user SwiftUI.

Please tell me this is not the case.