Overdrain Cup/Basket In Sand Filter

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What's the purpose of an overdrain cup and basket/strainer in my American Meteor sand filter? See attachements - parts 9 (cup), 10 (basket), and 12(kit). Also, there is a closeup of the two parts.

While replacing my valve, the basket disintegrated. The basket holds the cup tightly against the underside of the multiport valve. The stand pipe is still perfect, and the overdrain cup is still in good condition.

So far, I have not be able to find the American (Pentair) basket (51030100) or kit (55025200).

What would happen if I omitted them during reassembly?