As for "backup hotels," a lot of the ones not in the block have "reasonable" rates; for example, the Sheraton at Keystone Crossing has a 2 Queens room for $177/night for Wednesday arrival/Monday departure.
Went to the archives of Gencon. For 2019, there were 16 Hotels to the North, 4 East, 12 West, 0 South, 27 downtown. 2022 is 33 downtown, 9 west, 0 South, 2 East and 1 North. Different of 14 hotels or so (I'm not double checking my math).
So, looks like the North really took a hit. Maybe with the extra hotels downtown and possibly more rooms, the net rooms are the same so.. the north wasn't needed for the block?
VIGs have been busy. Crowne Plaza is already sold out. Westin, Fairfield and Embassy Suites are out of queens.
Perhaps you're looking at a weird date range or something?
It seems like the Wednesday inventory is low. Weird.