I select bones and select all keys of those bones in the dopesheet.
I go to the first frame in the dopesheet
I select the [ / Adjust ] button to adjust the values of all selected bones/keys based upon the adjustment I will make on first keyframe
I adjust the position of all bones on that first keyframe
I note that all of the position/key values have adjusted relative to that move (this is good)
If I scrub the timeline, I note that the tangents of those keys have been 'left behind' and all of my inbetweening is ruined (this is bad)
Adjust should move the tangents along with the keys, please.
If I'm missing a step, please advise.