You are misleading again, miners on Ocean arent building the entire template. Miners connected to Ocean are being being told what coinbase tx to use in their templates. If they choose not to use the one Ocean provides, they are switched to solo mining, which removes all variance reduction benefits, which is the entire purpose of pool mining. Ultimately no tangible decentralization is achieved because Ocean (being a centralized trusted third party) can be pressured by regulators to censor, just like any other centralized pool can.