So you were able to make the hidden label under the food description with Alt+F, and also put an Alt+F on the unattached label up top without getting a warning message?

Yes, pretty much that.
I just had another database open and put a hidden label under a combo box in a continuous form.
The label in the form header is labelled ‘Film’ – and now ‘&Film’, i.e. underlined.
Alt+F lets me jump to the ‘Film’ column with the corresponding combo box.
And renaming the label in the form header (to ‘&Film’) works without Access throwing up a warning or anything like that.

Whereby:
I have to restrict this when I look at the label in the form header in the design view again.
The green triangle with an exclamation mark is already there.
My German version of Access tells me: ‘Key combination error. Unrelated label field with key combination’ [translated].
But such error messages are common in this area anyway and can actually be ignored.
And I didn't even notice it earlier. ^^