It does if and only if that's what you reduce extremism down to.
There's enough there to assert a quadratic relationship (in a given regime) with _their particular phenomenological measurement_ of extremism.
In the physical sciences we can often get away with ignoring the difference between what a measurement procedure outputs, and what it is measuring. But this only because we have high degrees of repeatability, and concordance with other ways of measurement. Neither has been shown to apply here.
The reporting of this is made worse by the use of a common term, rather than the diagnostic tool. Yes, there are common meanings of "energy", "momentum", and so forth, but people understand that they mean very specific technical definitions when a physicist uses them.
