The main issues I see with using this for any type of nutrition insight is that the vast majority of people that buy groceries are:

1 - buying them for more than themselves (e.g. family, partner, etc)

2 - You don't eat all of the groceries you buy every week. 1 bag of sugar may last a year.

3 - grocery receipts are really long and awkward to take pictures of.

4 - It doesn't take into account other food/nutrition you get outside of your home.

5 - The huge rise in curbside grocery orders means far fewer physical receipts

6 - Nutrition is very, very, personalized. There's not an effective way to make meaningful nutrition suggestions.

I suppose this could be useful to scan for any specific allergens, like if any of the groceries you purchased contain nuts or something. I love the idea of gathering stats about what you purchase though, whether it's food or not. I just assumed my regular grocery store (who are basically a tech company) could do a better job at tracking this than I ever could.