The motivation behind doing it was that different cultures treat what is food differently as is exemplified in their example of chicken feet. However, that also raises big questions on the efficacy of this data since houses which use raw fruits and vegetables are probably likely to have higher food waste by this definition since most people aren't buying bone-in meat. But since a big objective of their report was tackling greenhouse gas generation from said food waste, I guess it makes sense in that context? I tried to figure out the exact methodology by which they estimate their numbers but I wasn't able to find it.