True, though BTC went through a similar "one mining pool has nearly 50% of the total hash power" a couple of years ago the community rallied around to fix that. Some people by moving their hash power into other pools. That was back when there were a lot of small miners and they could make profits without having to buy into the economies of scale that come from a mining farm. That's no longer the case for BTC, and appears not for BCH right now. Until the other miners come along, the proportion of blocks going to two miners does reduce confidence in BCH.