@Milhouse
The settings of the sidechain (i.e. the side chain filter) are linked/matched when gate or compressor processing is ganged, it is only the sidechain souce which is not.
In much the same way as you might want to match input or direct out trim, but not change the input or output sockets being used.
However, a workaround if you are using lots of different sources for ducking and are constantly needing to change these (which I presume is the case as it’s the only time I can see it being a problem to alter multiple sidechain sources), would be to leave the sidechain fed from a mix, then change what you are sending to that mix on a scene-by-scene or ganged routing basis.
Hope this helps!
Keith.