Read the thing, it explains that their "perfect shuffle" isn't every card being perfectly interleaved (yes that'd be deterministic).
But rather, at every card, there's roughly 50/50 chance of it being a card from left/right piles being dropped, with an increasing odd for the bigger pile.

I haven't bothered proving it, but I'm pretty sure a perfect intellect interleave would eventually put the deck back in order, but that's not what the article is discussing.