well like you said it applyed to pool operator which are the one that give money to the miners, so in that case for them below 600 there is no tax to pay
Please stop confusing people and providing bad information. The $600 is a form requirement, nothing to do with taxes. For the miners, it's income, they declare it and pay taxes no matter the amount. For the pool operator, it's gross income so would be declared in their P&L, but the payouts are a business expense so would reduce net income and corporation taxes.