I'm convinced it must go way back in their ancestry - if they can see the bottom of the dish then it's empty! Trouble is when Katy does this it's because she cannot see and if she's licking the bottom of the bowl, it has to be empty. All I do is scrape and food from the sides to the centre and she happily accepts that...
As an aside, have you tried the Gourmet Soups from the Brit shop? No idea if they all sell it but I get mine from Corner Shop. If there is any wet food which has been left in the dish and which may have dried out a bit, it's perfect to put a bit from the sachet over it and it goes in no time. I think KatyKat's sense of smell must be heightened since she became blind as she smells the soup as soon as I open the sachet.