because you know the stress syllable by looking at the word. take Desert and Dessert, do we say DES-ert or des-ERT. Also in portuguese, at least, I can know which "e" sound [1] each "e" in the word makes by knowing this (well, almost, but not completely, but much better than English.)
RTS games are fairly unique in that you always know you could be doing things slightly faster, constantly. Yes, you can make a big mistake that loses you the game (like losing a queen badly in chess), but often if you just did your macro tasks a little faster you would have won, or scouted every 30 seconds instead of 35. The article touches on this in respect to APM.
We have a related problem in the UK. Sometimes very small "country lanes" have no explicit speed limit, so defaults to national speed limit of 60mph, which you would have to be suicidal to drive at (or just hate your car), but Google maps still often route finds along these roads.
[1]: https://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio