It makes sense, in that they want 1/2 oz plating over 1/2 oz foil as a base copper.  Any final finish specification (ENiG) should be a separate note, as the notes refer to 2 different requirements.

It doesn't make sense, in that the foil/plating ratio shouldn't matter to the customer (except in very rare cases), but it DOES make a difference to the fabricator.

I have just finished updating our very old boilerplate notes.  One of the changes was to remove the foil/plating note, very similar to the one you referenced.  Our vendors regularly complained about not having the option to use what was best for their process.  We now only specify finshed copper thickness.  I have no idea why that was originally done, other than the possibility of having some control over hole plating.  That also isn't really required, since IPC-6012 was always specified anyway, covering hole plating minimums.

Pete