I tried it in Firefox and Chrome, but changing the SVG shape did not change the favicon displayed on the tab. I don't think I understand what you meant.

PS: This submission of mine is at least a day old, but it now shows as posted about 3 hours ago; I presume this is because it is from the second-chance pool.

I think they meant it as a feature suggestion (given that it should be easy to implement since SVG files can be used as favicons).