I believe your parent poster was just poking fun at the "if everybody started to do X" construct. If all humans started to use EVs (or any other type of vehicles) at the same time, the traffic jams would indeed be horrific. At any given time perhaps <5% of people are on the roads, so how would you even fit 100% of people onto roads at the same time?
Oh, didn't cross my mind. I think you are right and I probably misinterpreted the comment. My brain went straight to it being about running out of power and causing jams, probably because it was such a common fear with regards to EVs (and still is to an extent, CC Bill Gates and Porsche/Tesla in 2020).
It was just a teasing comment about these devil's advocate style of comments being non-sensical and counter productive, and often in favor of some incumbent which normally receives pretty fair criticisms.
