The current implementation allows to insert embedded images and windows in a disabled text widget, try this script:
The documentation says:
If the widget is disabled using the -state option, then its view can still be adjusted and text can still be selected, but no insertion cursor will be displayed and no text modifications will take place.
This statement is not fully clear, but the insertion of embedded images/windows is a text (widget) modification, so it is not allowed. At another place the documentation says:
Specifies one of two states for the text: normal or disabled. If the text is disabled then characters may not be inserted or deleted and no insertion cursor will be displayed, even if the input focus is in the widget.
Due to this statement only character insertion is disabled. But this is not logical, why the insertion of embedded images/windows is allowed in disabled widgets?
Because it's a bit unclear, and for compatibility reasons, the revised implementation will allow the insertion of embedded images/windows in disabled text widgets. But the documentation has to be clarified.
By the way: the current behavior, that the widget is silently ignoring text changes, if the state is disabled, is quite inconvenient. The developer has no feedback what is going on. It would be more convenient if an error will be thrown when trying to modify a disabled (or readonly) widget. Of course there is one problem here, some older applications might not work after such a change, although this can only happen if the affected application has bugs (inserting text into a disabled widget is a useless operation, and this can be interpreted as a bug).