No - comment was in the opposite sense. The only way the file would be seen as locked by the user is if you had used some of the "extra features" in your layout.
I just downloaded your Friesach file, opened design mode, and you have used a picker, which is an "extra features" pack item. So you have the pack, and anyone wanting to edit the layout will need it also. If they don't have it, the have no option to open design mode.