I've got to say that the scientists involved in this speculation don't seem to have spent much time around the toothless.
Babies and elderly people who need a ground/mashed diet need it because other textures pose a choking hazard. Many an old party will happily gum away on just about anything. The difficulty is in the embarrassment factor at mealtimes. I doubt the creatures under discussion gave table manners much thought.
I think the key factor in the analysis is that the person in question lived in Georgia, a country just south of Russia, with a climate which is very cold in the winter, well below freezing.
1.77 million years ago predates agriculture by quite a bit, by about 1.76 million years or so.
Modern toothless humans can eat ice cream, cereal, baby food, crackers, bread, etc. These did not exist 1.77 million years ago. So, what did he eat?