Please choose:
Delete the email. It was sent by mistake. Getting involved will look political and could put your own position at risk.
Raise it quietly with your HR business partner first. Get clarity on the system before involving your team.
Raise it at the leadership team meeting on Thursday. Ask who approved this system and what it is being used for.
Do Thursday — and then tell your team on Friday. Transparently: "I found out this week that we are all inside a scoring system none of us knew about. I want you to know what I know. And I want us to decide together what we think about it."