Similarly random promotions have been killed by OnePlus in the past much faster than that, so it’s probably smart to hurry up and get your order in as soon as possible.
If you miss out on this super-rare promo, can’t make it work for some reason, or simply want to take your business elsewhere, both Best Buy and Amazon are still selling the unlocked Nord N20 5G at the more “typical” $70 discount with no strings attached and no special requirements whatsoever.