Miners can not operate anonymously nor do anything useful with selfish mining or double spends as long as they are mining on pools, which the huge majority of the hash rate is currently doing.
Incorrect. Just by being on a large pool, they inherently are mining on the correct block more often than the minority of the hashrate, which instead have to wait for propagation delay.
Also a mining farm mining (or oligarchy of them) with 33% of the hashrate even if mining on a pool, can still do the selfish mining attack without informing the pool. Remember Bitcoin never implemented Meni Rosenfeld's oblivious mining shares fix to prevent share withholding attacks. This is assuming the pool supports
getblocktemplate so the miner can set his own transaction block hash (however I guess most pools would do something to prevent a miner from pool hopping so I am not 100% sure about this).
Also miners could own the pool and pretend not to. They could obscure their selfish mining by hopping around to different pools they own. You can bet mining farms have looked into all these techniques. The Chinese are very clever.