favicon(ファビコン)は512x512も用意しなければならない?

ファッ!?

For Chromium, you must provide at least a 192x192 pixel icon, and a 512x512 pixel icon. If only those two icon sizes are provided, Chrome automatically scales the icons to fit the device. If you'd prefer to scale your own icons, and adjust them for pixel-perfection, provide icons in increments of 48dp.

Add a web app manifest (Nov 5, 2018 — Updated Sep 14, 2022)

言及されているのはここですね

HTMLでのマークアップは

<link rel="icon" type="image/png" sizes="512x512" href="icon-512.png">

の様な感じでもokだと思います。

関連情報:
Adding favicons in a multi-browser multi-platform world - mobiForge
https://mobiforge.com/design-development/adding-favicons-in-a-multi-browser-multi-platform-world