The game itself prevents you from guessing words that aren't in the 12972-word list. It doesn't count as a guess, and doesn't go through. So if you want to try anything with a larger list, you're playing something Wordle-like, not actual Wordle.

But I agree that using the 2315-word list is basically cheating. On the other hand, are words in that list more common English words than words in the 12972-word list? If so, then humans in a sense intuitively take advantage of the 2315-word list by guessing more common English words rather than infrequent English words. So since humans sort of use the 2315-word list intuitively, it sort of makes sense for a computer to use it as well.