The stated problem bounds do not include being able to tell whether someone controls >50% of the hash rate. That isn't in the paper at all. The wording of the paper is "As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network". It doesn't matter whether they cooperate via pools or otherwise, either way it is outside the bounds.
Without considering the Sybil attack, then one isn't solving the Byzantine fault issue, i.e. isn't solving the Byzantine Generals problem (which is the correct title of this thread). Just because Satoshi failed to mention that he hadn't solved what he was implying to have solved, doesn't make that just having a majority of the hashrate is the only consideration in a PoW solution to the Byzantine Generals problem.
There is no Sybil attack possible on the problem
as stated. "A majority of CPU power" is a physical quantity which can't be Sybil attacked. Period.
This does not mean that Bitcoin will be a great success and moon to $10 million/BTC, or even that it will survive at all more than another year or two, or anything in between. It is possible to conclude that the consensus algorithm does exactly what Satoshi said it does (putting aside possible selfish mining attacks), and still conclude that such a security margin is too weak to be
useful, because of all of the ways the precondition itself can fail (pooling, of course, can contribute to some of them).