Well if they have overcrowded the mining environment that does not allow the smaller outfits to compete for the amount of coins available to mine. Then yes they are controlling how much is available across the board. Essentially hording all the available power to mine those coins available.
I have the same thought, if they are mining major part of bitcoins, they have a lot of coins in head, if they hold all of it, they can control the price and for sure they will mine for years and years, none can compete with it. In some way this is good for all holders.
Number of Users makes ZERO Difference, BTC by itself is a worthless token.
The ASICS (BTC Mining) does all of the work and is where the Value of any PoW truly is.
Let me put in simple terms since so many seem clueless on what a 51% attack really is.
China has over 51% mining, that Centralizes it under China's Control, (for over a year)
This allows them to accept or deny any transaction or Double Spend (Counterfeit Coins) at will.
FYI:
Funny how the clueless or corrupt like to pretend like China does not rule BTC.