> It's too easy to misjudge who's accomplishing what if your only input is observing who speaks up the most in meetings, who's the most talkative in Slack, or who spends the most time putting together presentations.

I would assume that it is the direct manager of the team that makes that decision or at the very least provides input.

And if you are managing the team and don't know who is accomplishing what, then you are in a whole lot more trouble than just a problem of choosing wrong strategy of splitting the team.