These particular potatoes won't be wasted.

But other potatoes likely will be.

It's not like people are suddenly going to want more potatoes.

There is some elasticity of demand. Some people will eat more potatoes and less bread or rice. Other people will fill up their cupboards; just because the farmer doesn't want to store these for later doesn't mean that individual consumers won't.

A lot of people will have a few more potato-heavy meals if they happen to have more potatoes. This means they'll (presumably) buy a little less of other ingredients for a spell, and maybe we'll end up with more of those going to waste, but it's definitely possible for that not to happen. Seems like a ripple of delayed food purchases of dry goods can be absorbed by reduced production far, far down the line.

Joke’s on you, got an air fryer for Christmas and I’m roasting potatoes every day, never bought so many potatoes in my life. They’re absolutely delicious.

Lots of people are price-sensitive to groceries, and will eat more potatoes if some of them are free.