It's coming back to me...
I was attempting to use a spline to control the movement of a character (like a puppet being controlled by strings).
I don't know where that project file is but here is a proof of concept I just put together than does reorient a bone based on the position of one of two (or both) CPs.
The project file consists of a two CP splines with subgroups 1a and 1b. (in the original project I believe it was a three CP spline with Start, Middle and End)
Both subgroups together are named Controller because it is the one that will receive the Group constraint.
Moving the subgroups/CPs about in the Chor moves and orients the Bone (that other than the Group constraint targeting the Controller currently isn't attached to anything)
A downside of this approach is that I'm not sure how to view CPs and Bones simultaneously.
I'm sure we can but my brain isn't working there either.
There was some cool stuff I was approaching but I stopped dabbling for fear of hurting myself in the process.
I do recall that a nifty thing I ran across was how to control things (objects) with one single solitary CP.
This was actually a trick of sorts in that there was/is a second hidden CP.
That hidden CP never moves, never changes orientation, never gets seen and leaves all the fun of animated movement to that other (visible) CP.
Edit: I am reminded of one reason I moved on from this R&D and it is that A:M unhides the hidden (orphaned) CPs upon reopening the model (it must assume that we messed up in hiding it because why in the heck would we want a single solitary CP?). But it works well until we save. The impetus for this single CP exploration related to playing with some point cloud type operations in A:M.