What do you mean by "recycles Bitcoin’s hashrate"?

Blockhashes of KMD is securely written to the bitcoin blockchain and further that data is used by the consensus logic. Basically the KMD blockchain data is extended to include small amount of the bitcoin blockchain.

Once the bitcoin blockchain confirms the tx with the KMD blockhash, then it becomes as secure as a bitcoin block as the bitcoin blockchain would need to be reorged for the KMD chain to be reorged.

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