Producing fraudulent blocks (ie, containing double-spends) is the same as "discarding all the hashes" because the consensus mechanism (the fork choice rule) will ensure that the block is rejected, unless the attacker can also provide 51% of the current network hashrate to force this bad block into the canonical chain.

I defend PoW as the most secure consensus protocol for the major public blockchains precisely because the cost of an attack is so high right now. The wastefulness of PoW guarantees that there won't be reason to get involved in the mining business unless one intends to produce valid blocks and get paid for it.

edit: I would argue that producing fraudulent blocks is a "strictly dominated strategy" in game-theory terms, because its outcome is always worse than following the protocol rules and producing a valid block. From that perspective I believe it is the same as "discarding all the hashes".

> Producing fraudulent blocks (ie, containing double-spends) is the same as "discarding all the hashes"

no, it's not the same, it has the purpose of Producing fraudulent blocks. you're contradicting yourself within single sentence..

> The wastefulness of PoW guarantees

there is no wastefulness. there is energy consumption with purpose of securing the blockchain.

it would have been wasteful if difficulty was fixed and miner was spending 100 times more energy than necessary to create a block every 10 minutes, but since difficulty adjusts - there is zero waste in PoW. every joule spent was necessary and provided value.