multiple physics caches allow for unique start/end frames but not unique drivers

As written in this report ...

In a multi-cache simulation, I can set separate start/end frames, but a driver is shared by both cache settings.

I need to cease a physics simulation for a series of frames, and possibly re-bake the simulation when I adjust the animation by scaling areas that will include certain timeline markers. This will also allow for correct re-bakes from command line, driven by timeline markers.

To achieve this I create two caches with appropriate stop and stop times:

These start/end times appear to be set per-cache, and all python methods return point_cache.frame_end as expected.

Now I want to drive the start/end frames from timeline marker names and problems begin. If I add drivers to start/end of both caches end edit in Drivers Editor, I can see that the cache names are distinguished in the editor, but changes to the first or second caches driver variables:

are then forced upon the other caches values:

This is inconsistent and requires extensive scripting to retrieve values like scene.timeline_markers["cease_movement"].frame to re-synchronize to any changed markers.