smarter autoheight for ordinal scales?

autoHeight with the default round:true option sometimes leaves too much white space. In the chart below it returns a value of 580, when ideally it should be 556px.

Plot.plot({
  x: {
    percent: true,
    label: "Frequency (%) →"
  },
  height: 556,
  y: {
    label: null
  },
  marks: [
    Plot.gridX({interval: 1}),
    Plot.axisX({anchor: "top"}),
    Plot.axisX({anchor: "bottom", label: null}),
    Plot.barX(alphabet, {x: "frequency", y: "letter", fill: "steelblue"}),
    Plot.ruleX([0])
  ]
})

Reproduce the supplied Plot example with autoHeight and the default round:true option, comparing the returned 580px height with the intended 556px. Trace the ordinal-scale height calculation and add coverage showing that autoHeight avoids the excess whitespace while preserving rounded heights where appropriate.