Who read article like this on mobile? In a pinch, I'd just activate Reader Mode (Safari, iOS), or more likely save it for reading on a bigger screen (tablet, laptop,…)
Read it on iOS Safari, without reader mode. Worked great.
Only thing that annoyed me is that there are very lengthy appendices. Thus the scroll bar suggests the main article is much longer than it actually is.
This page doesn’t specify _any_ font size. It relies on your browser to choose an appropriate size instead. If the text is too small for you to read, then your browser settings for default font size are wrong.