I haven't actually tried this, but I've read that there is an "Engine Forced Activation Mode". The procedure I read calls for setting the parking brake, with your foot OFF the brake pedal and the car off, hit the Start button twice, then (while in Park), press the accelerator twice, shift to Neutral and press the accelerator two more times, shift back to Park and press the accelerator two more times, and then put your foot on the brake pedal and hit the Start button once. You need to do all that in 60 seconds or less.
Interesting info to try.
I am an Occam's razor kind of guy though. All those steps, or have someone else press the gas pedal.
An example, when you change the oil in the Niro, I just open the maintenance screen, scroll to the maintenance interval, then hold the ok button to reset it. I don't have to find out how to do it in some youtube video, or this forum, or the dealer, it just right there nice and easy.
My truck though, every time I have to reset the oil service due light. It's "pull your ear, stand on one leg, hop 4 times, switch legs, hop 6 times, turn around clockwise 2 times, lean forward, lean back, eight times."
But to reset the mpg, just tap the right arrow.
As for taking off the "elbow" and making the car go into limp mode, as soon as you turn the car off, and then put the hose back on, the ECU reads that it's working again, and the code goes away.
As for your question as to why to do this...
Just search GDI intake valve cleaning.
It's a 3 design combination.
3-GDI, this is by far the biggest reason why. There is simply no cleaning from the fuel on the intake valves.