I disagree with this analysis.
I have explained my point in much greater detail here as a separate topic in the main Bitcoin general forum:
The Bitcoin consensus mechanism is incorrectly labeled Proof of Workhttps://bitcointalk.org/index.php?topic=1176835.0Well I guess I must agree. Thanks for making that point.
Edit: let me add that for as long as the individual miners can't decide what they put in the block for their mining shares, then my statement that the entropy of proof-of-work is unbounded needs to be corrected to bounded, which is the same as for proof-of-stake.