> you can just manually make any letterform 2x width,
Yes. Any glyph may be wider than its advance. The advance, however, must remain the same across all glyphs. If it does not, the font is not monospaced.
The passage you’ve quoted refers not to the width, but to the advance.
> you can just manually make any letterform 2x width,
Yes. Any glyph may be wider than its advance. The advance, however, must remain the same across all glyphs. If it does not, the font is not monospaced.
The passage you’ve quoted refers not to the width, but to the advance.