Nope, HN's CSS accommodates smaller screen sizes [1]:

    /* mobile device */
    @media only screen
    and (min-width : 300px)
    and (max-width : 750px) {
      #hnmain { width: 100%; min-width: 0; }
      body { padding: 0; margin: 0; width: 100%; }
      td { height: inherit !important; }
      .title, .comment { font-size: inherit;  }
      span.pagetop { display: block; margin: 3px 5px; font-size: 12px; line-height: normal }

[1] https://news.ycombinator.com/news.css

Nope, your snippet proves nothing. The only font rule in it is `font-size: inherit`, which means "don't change the size." So your proof that HN resizes text is a line that resizes nothing. Since your snippet was so useless I had to go read the actual news.css to find out what rules are actually there. The result: body text goes from 12px to 13.3px.

It's still small. The widely considered standard size of body copy is 16px or 1rem.

But the thing is, which was my point all along, it doesn't fucking matter.