> It's hard to imagine that using a typical suite of PNG images at different sizes is going to be more efficient (and future-proof) than a single SVG file run through svgo.
That's the wrong comparison though - each browser will typically only download one favicon size.
The post you linked to doesn't include the word "SVG". Is there a separate article that compares using one SVG file vs. using multiple images?
It's hard to imagine that using a typical suite of PNG images at different sizes is going to be more efficient (and future-proof) than a single SVG file run through svgo.