Fairly normal in larger organizations, has been the case in my past 3 jobs.
The idea is to reduce gamesmanship in promotion decisions (my whole team is senior engineers, etc.), and to provide some uniformity across the organization. They usually also have some budgetary discretion as well, as they have to balance whatever pool of money is available for promotions, COL adjustments, and merit based raises.
Fairly normal in larger organizations, has been the case in my past 3 jobs.
I guess my last several orgs just kept that away from me then, for whatever reasons they had. It's honestly surprisingly new to me that "committees" for such a thing are "normal" at large orgs.
In those cases, I had a lot of autonomy over promotions-as a leader, other than the usual "get approval from the CFO for funding if there is a raise involved"; beyond that, coordinating promotions with my director what the promotion would entail was all there was to it.
The idea is to reduce gamesmanship in promotion decisions (my whole team is senior engineers, etc.), and to provide some uniformity across the organization. They usually also have some budgetary discretion as well, as they have to balance whatever pool of money is available for promotions, COL adjustments, and merit based raises.