Tooltip.positioner function not working

[roryhill]

Hi,

By default, a Highstock line chart displays two tooltips on hover: One for the y value, positioned at the closest series point; and one for the x value (positioned at the bottom of the chart). For my project I would like the y value tooltip positioned at the left of the chart (similar to how the x tooltip is 'anchored' at the bottom), but the tooltip.positioner function doesn't seem to get called.

StackBlitz example

Working JSFiddle (Not how I want the tooltips to be positioned, but a simple example of the working tooltip.positioner)

Thanks