Using the mark sort option excludes other marks' values from sorted domain

[mootari]

I'm filing this bug with the caveat that it might be expected behavior.

Given two marks that render different sets of values, if the first mark defines a sort option then the sorted domain won't include the second mark's channel values.

The following example:

Plot.plot({
  marks: [
    Plot.dot([{k: "b", v: 1}, {k: "a", v: 2}], {x: "v", y: "k", sort: {y: "x"}}),
    Plot.dot([{k: "b", v: 1}, {k: "c", v: 3}], {x: "v", y: "k"}),
  ],
})

extends x to include {k: "c", v: 3} but does not extend y:

[mbostock]

WAI

[mootari]

Where is this behavior explained?