Except it is well known that Bitmain mines with its shovels before selling them. People have reported receiving their machines with dust in them and you can see the changes in mining difficulty corresponding to when they in-house mine and then ship the ASICS out.

Anyway, Bitmain better watch out. Cryptocurrencies are now regularly implementing hash function changes. GPU mining is dying, but not to ASICs but to the more configurable FPGAs instead.

It is not the strongest that survive, but the ones most responsive to change.