Vega-Lite: Trying to combine selections

I am trying to create a set of charts that use two types of selections:

• overview + detail (example), using a selection on the bottom chart to drive the scales in the top chart.
• tooltip rule (example), using a hovering selection on the top chart to show a vertical rule that can be used as a tooltip of sorts.

As you can see, this works - sort of. The problem is that the tooltip in the second selection seems "unaware" of the scale change from the first selection.

Three possibilties I can see here:

• Am I doing something wrong?
• Am I trying something that is not meant to work?
• Is there a bug in Vega-Lite?