https://github.com/neo-project/neo-plugins/blob/db04e756a64c149e86d117fe89879c72f319c7df/SimplePolicy/SimplePolicy/config.json#L5
It causes a problem for ClaimTransaction.
For ClaimTransaction, people can't add network fee to it because it's set to zero, which means every ClaimTransaction is free transaction.(https://github.com/neo-project/neo/blob/7883e587a9448330d21669ebe748402871da3a50/neo/Network/P2P/Payloads/ClaimTransaction.cs#L16) Besides, the size of ClaimTransaction is usually larger than 1024. If we set MaxFreeTransactionSize to 1024, all ClaimTransaction will be influenced. If we make MaxFreeTransactionSize larger than 1024, then it's a meaningless configuration item. We get a paradox here.
Another thing is We can't prioritize ClaimTransaction anyway.
(https://github.com/neo-project/neo/blob/7883e587a9448330d21669ebe748402871da3a50/neo/Network/P2P/Payloads/Transaction.cs#L52)