I did not get your point either, but now it makes some sense.
This why, IMO. Because the US has no Far Left to speak of. Which means that Far Left in the US corresponds just plain Left, even moderate Left Social Democrats.
There is nothing, for example, like the Shining Path in the US. Or even the old Weatherrmen, of long ago, hippie days. Those truly Far Leftist indeed are cut from the same mold as those on the Far Right. A few of the modern so-called Antifa active in Portland, etcetera, might qualify as true Far Left. Those people are few.