Which SPOs would have lost rewards? The ones running the new node, because the blocks with too-cheap TXs would have ultimately been discarded, or the ones still running the old node, because they would have forked the chain discarding the in their interpretation wrong blocks, but the new nodes would have continued? Or would it have depended on who is the majority?
You cannot tell (as it depends on), always those who lost the fork battle (longest chain wins always).