i completely disagree with this idea..
this uses the assumption that a person would use all 8 functions, meaning that none of his functions could compare to someone who has fully developed a few prefered functions- so effectively this person would seem a bit thick, i've honed Ne since i was a small child, and using practiced Fi and Te i see the world as a very complex pattern which i've developed over time and maturity, a 50/50 person would be too distracted to develop this, and wouldn't even be as good as Se's at sensing either, or any of the other things.
you can't access several functions at once, you're moving from one to the next, e.g. ill be applying judgement about something using Fi, and afterward will realise that Te leads me to a different judgement and follow that thread. so this person would be moving through many different functions all the time and would contradict him/herself.
all you'd get is a "slow" contradicted person. or the person will be shaped into using the functions which their parents, friends and society expect of them. they wouldn't catch up until old age.
-they'd only be able to offer contradictory immature Fi or Ti or Te or Fe judgements for example.