The primary reason for the parboil is to be to lighten the color of the potatoes and prevent off flavors by flushing away excess starch. It's not strictly necessary to get a decently crispy chip. That said, par-frying isn't likely to be as effective for this purpose, per this passage from your linked source:
...heating up starch granules in the presence of water causes them to
absorb water and expand. Eventually, like little water balloons, they
burst, expelling the starch into the water where it can be safely
dumped down the drain.
With frying, you might wind up bursting some starch granules, but because the starch isn't getting flushed anywhere, it will remain in the potatoes. This may actually further the development of browning and off flavors by raising the concentration of starch (though you may denature some of the enzymes that are also responsible).
I think you're also likely to see some unintended side effects from par-frying. For example, partially cooking and doing damage to the cell walls could cause the chips to leach moisture and starch. As it cools, that could cause the chips to stick together if you're not very careful about keeping them separated. It might also cause some of the excess oil from the surface to seep into the interior, making your chips greasy.
If your objective is first and foremost maintaining a consistent oil temperature (which is a worthy goal) then the best solution is to fry in smaller batches and allow the oil to come back up to temp after each batch. This will take longer, but it will still probably be a time savings over doing a whole bunch of par-frying the night before and then finishing them off at the event.