Yes. I’ve been doing webdev for 21 years and WP for 12 so well aware.
I”m just letting you know this option has proven to be best solution for “most people” who don’t know how to properly specify https font loading, or may not understand how web-safe font stacks work. Some older default OS fonts also are not as well optimized as modern fonts — so, loading a TTF wont when a WOFF might be better is one example.
If you think it’s bug post a note on GITHUB.
It’s not a bug, and so if you don’t need support here, then opinion posts don’t do much. You can, of course, roll your own solution. But this is how this plugin works. It works for our news portals and static site also 100%, so we’re getting pages served by Google and have green bolt icon in SERPS, so guess it’s working for us ??
Technically you may be correct, but this solution *does* work well for mobile users and is currently being used by large high-traffic WP VIP sites without issue. You don’t have to use it, if you don’t want to. And again, you can spec out your own fonts if it makes your life easier.
(( I don’t work here … this is just an opinion as an early adopter of AMP tech on dozens of large news portals ))