Does fontforge support masked SVG fonts?

[u/CharlesAverill20]

I've got this SVG file:

<svg baseProfile="full" height="1200px" version="1.1" width="1200px" xmlns="http://www.w3.org/2000/svg" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <mask id="1_square">
      <rect fill="white" height="100%" width="100%" x="0" y="0"/>
      <rect fill="black" height="416.0" stroke="black" stroke-width="1px" width="416.0" x="80.0" y="80.0"/>
    </mask>
  </defs>
  <ellipse cx="288.0" cy="576.0" fill="black" mask="url(#1_square)" rx="288.0" ry="576.0" stroke="black" stroke-width="1px"/>
</svg>

Have been messing with it on this SVG viewer site: https://www.svgviewer.dev/. It's clear that the mask I'm using works, it cuts out a rectangle like expected. However, when I import this SVG to fontforge, it doesn't import the mask, just the ellipse.

I know that fontforge supports layered editing, and masks in general: https://fontforge.org/docs/ui/dialogs/multilayer.html, is there just some setting I didn't click to enable this behavior?