SwiftUI TextEditor unaffected by .textCase() modifier

In the following code, three of the four modifiers on TextEditor work as expected. However, .textCase(.uppercase) seems to be ignored. It does not force entered text into upper case.

TextEditor(text: $document.text)
     .textCase(.uppercase)
     .font(.system(size: 18).monospaced())
     .scrollContentBackground(.hidden)
     .padding()

I can find nothing in the docs that indicates TextFields do not recognize this modifier, and the code compiles just fine. Any thoughts?