Missing item anchors in pie charts

[esposm03]

Citing from the manual for the piechart function:

The chart places one anchor per item at the radius of it’s slice that gets named "item-" (outer radius) and "item--inner" (inner radius), where index is the index of the sclice data in data.

Given the above, I would expect to be able to use an anchor like item-1 to reference the chart slices; however, the following code panics with Anchor 'item-1' not in anchors ("default", "chart", "legend", "center") for element 'pie'

#import "@preview/cetz:0.3.1": *
#import "@preview/cetz-plot:0.1.0": *

#canvas({
  import draw: *

  chart.piechart((1, 2), name: "pie")

  line("pie.item-1", (2, 0))
})