Just because that's the market share of btc.com and antpool it doesn't mean that's all the hash rate Bitmain has at its disposal.
11% of the blocks are unknown, it could be anybody.
Viabtc with 9% has received investment from bitmain, btc.top with 7% is a private pool, nobody really knows what's going there and the ower is a bcash fan.
So, in reality, it could be way more than 50% even now, and they might be doing this simply to prevent people from talking about a 51% attacks.
ps.
Don't forget the 3 exahash mining BCH (about 5% of BTC hahrate) that is 99% owned but Bitmain.