Thanks for the link, interesting stuff.
So yes that's mainly unknown tokens, chains that forks from popular chains. Also 51% of hashrate from a pool doesn't mean malicious actor to easily do a 51% attacks. While the pool dominance isn't an ideal situation it's usually not as bad as some people like to tell.
But there is no explaination on how PoW is less secure than PoS chains (especially with most tokenomics launch), PoW is indeed a better design to recover from attacks.