Funnily enough this "one graphical unit" is rendered as two graphical units in my environment.
I wonder if it's a specific app or just something in Android not rendering the font correctly?
The level of ligatures requested in CSS makes sense for the site-supplied font. (I need to regenerate the fonts due to the table at the end of the article using characters that the subsets don't have glyphs for.) If you block the site-supplied font from loading, the requested level of ligatures may be excessive for your fallback font.