They use the same template for constructing blocks. Possibly. Not confirmed. Brains actually offers different payout methods and was one of the first to support stratum V2. They also pioneered stratum in the first place. Brains makes miner firmware, so naturally a lot of other miners will use the same firmware. But brains pool as mentioned above only controls 1% of hash rate. Also, I'm of the opinion that mining centralization is not a problem at all. There will ALWAYS be 1-2 big pools. That's just how the incentives work. It takes 2 seconds to point your hash to another pool. It's a non issue and people should be more focused on dependencies in core than anything to do with miners. Just my 2 sats