Whenever I hear about stories like this, I can't help thinking there's another reason that makes sense, but we're just not being told what it is.

What I'd expect would make more sense is that the store owners don't want to give food to food banks or homeless shelters because they don't trust their employees. They're concerned that their employees won't put that food out on the shelves for sale until it's "Best Before" date has expired, in which case it just gets donated to a charity. There may be store employees that are actively involved in charities that will do stuff like that to ensure their charity always has a lot of fresh food being thrown it's way.

By requiring the food to be discarded, you avoid the problem of employees manipulating the system to provide food to the charities of their choice at the store owner's expense. But, no store wants to say "We're doing this because we don't trust our employees." So, they come up with some BS about the government not being able to verify the nutritional standards, blah, blah, blah.