These aren’t contradictory. Throw away food that doesn’t have value through needed nutrition or net pleasure. At the point you realize this, the waste has already occurred—you don’t actually avoid the waste by eating it.
You should also plan as well as possible to avoid waste, but those decisions are made at a different point in time, with different levels of uncertainty about the future value of the food.
These aren’t contradictory. Throw away food that doesn’t have value through needed nutrition or net pleasure. At the point you realize this, the waste has already occurred—you don’t actually avoid the waste by eating it.
You should also plan as well as possible to avoid waste, but those decisions are made at a different point in time, with different levels of uncertainty about the future value of the food.