I agree that Text Fields need to be looked into. If I select a white background for the text field and I disable it, I expect a background color a little gray (maybe), but if I select red as background I don’t want to be the same gray when disabled, maybe a grayed out red (if there is no other option). In other words, that in Windows behave like in Mac (the text field background is preserved).
Matthew, I did some tests (before I read Julian’s answer), he is right, I think your Label is not fully inside the blue rectangle. You can be sure that the label is inside the blue rectangle if you right click on the label and you can see the Unparent option.
See my test, Label1 is not a child of the blue rectangle, Label2 has the blue rectangle as parent:
when the rectangle is the parent of the label, then you can see the Unparent option, if not, it will be grayed out
Hope this helps.