Ah, I stand corrected. The content box width is indeed based on the viewport size. My text, however, is still rendered in 14px Courier on macOS (and even given a .monospace class), so I'm not sure what's going on there.

I just updated to Chrome 79 and now the distilled mode is gone. For anyone who's looking on how to re-enable it, here's a thread: https://support.google.com/chrome/thread/22576539