> This is mostly true, but I guess they wanted to avoid scaling up 16x16 favicons into a blurry mess on iOS, so made icons specially tailored for the iOS homescreen into their own category.

Vista introduced dumping pngs directly into icos[1].

I think Apple went this route to avoid having to download the ico as it contains multiple images and is hence quite a bit larger than the e.g. single 57x57 png you are looking for.

[1]: https://msdn.microsoft.com/en-us/library/dn742485.aspx