If you copy and paste properties over a frame that has Text with multiple styles in it, all the text styles will be detached.
- Create a frame with two text layers, each with a different style applied.
- Duplicate frame
- Copy Properties (Ctrl+Alt+C) of the 1st frame (the frame being selected)
- Paste Properties over the 2nd frame.
- All the text layers will lose their attached styles in the 2nd frame.
No matter how deep the text layers are in frames or groups, every style will be detached inside the frame.
Colour styles will not be detached inside the frame = Correct behaviour.