I don't see how "spy mining" actually helps. It seems a bitter pill to suggest that now we need ANOTHER layer of validation on top of the existing protocol, further increasing Bitcoin's energy cost.

And if you believe this mitigates the attack, then "spy selfish miners" must also exist then, keeping parity.

Proof of work as implemented now is fatally flawed, and it's primarily a tenant of faith instead of logic that it isn't. Just google "selfish mining debate" and enjoy the plethora of inane and tedious reactions.

But also: yes the paper is not at all new. After replication and other checks, the Bitcoin community has gotten up on its high horse, plugged its ears tight with wax, and started signing, "I can't hear you!"