That article is strange. I was of the belief that most western "monospace" fonts were in fact "duospaced" under their definition. This distinction isn't apparent for normal writing, but such fonts usually make most emoji two chars wide. This is true at the very least for Adobe's "source code pro", which I typically use. It mentions the OP font as the only western example of such a font, but iA writer doesn't use integer multiples of the base width (necessary to qualify under their definition, as well as under common sense) for M and W.