If you add console shaper to your mix bus, it’s actually applied to every channel that is routed to the mix bus. It’s not applied summed, it’s applied at the source of each channel.
Additionally, you can add console shaper to any bus and then every channel that is routed to that bus has console shaper applied at their source.
But maybe you want an individual console shaper for every channel so that you can have different settings for every channel?