The flynn effect has long since stopped and has even started to reverse. Besides, it was never an increase across each category of measured intelligence, but almost purely an increase in symbolic logic, so the effect was particularly strong for those tests that depend on things like raven matrices.
IQ isn't a perfect representation of g, but the intellectual attack on its validity is motivated by (pro mass-migration) politics and those that still cling to the tabula rasa idea of education being the primary predictor/initiator of high IQs, though that idea is completely destroyed by anyone that has looked at any of the twin studies that show that there is no factor stronger than genetics on IQ. Though genetics account for approximately 0.65 of the correlation, we don't have any other determinant that is even a third of that (education + social class + wealth together amount to a correlation of about 0.1)
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As for the articles posted, the articles spout a lot of long disproven shit. If I read the actual refferenced study:
https://www.sciencedirect.com/science/article/pii/S0896627312005843 then if I am understanding it accurately, the study makes a case for measuring multiple factors rather than a singular number. Of course IQ tests already did this, except they take a new approach which seems to argue in particular for a two factor measurement of g.
In essence it depends on whether you conceptualised the discussion as being specifically about IQ determining voting rights, or "our best measurement of intelligence". If you divide it into multiple factors, you could still create a limit of those who would and those who wouldn't be allowed to vote.
Note, I'm not arguing for such voting law, I've already argued against it and still stand by that. But this attack on IQ doesn't really attack the fundamental concept of hierarchy of intelligence as a limit for voting rights, since I think an obvious and perhaps generous interpreation would be about that.
If you'd subdivide fast runners into fast starters and fastfinishers, you could still calculate a limit on who would be fast enough and who wouldn't be for whatever purpose you might want to create a limit/barrier there.