Its always been a minimum 10 day waiting period from time of purchase from what I understood.
Correct. There is a 10-day “cooling off period” from date of purchase in statute, but you could go to MPD with a receipt showing you purchased the firearm >10 days ago, and for people who had previously registered at least one firearm (meaning you passed their background check), they would turn around the new registration in 20 minutes. Apparently not the case any more, meaning more trips to 300 Indiana NW.