Yes, the Dec 1 date has been around for a while. The change happened in 2021 when IDFG implemented NR zone specific quotas. Prior to that, if there was a NR tag available out if the ~12,000 NR tags, it could be purchased for use in any uncapped (or capped, if the cap had not been reached) zone. After 2021, each zone had had a quota of NR tags available. Contrary to all the talk of increased demand and blaming it on social media influencers, this policy change solely created the 12/1 circus, nothing else. It really started to snowball when guys would finally get in, see that their top choices were gone and panic buy a tag in a zone that they would have never bought a tag in previously, making that tag unavailable residents come August of the next year.
Anecdotally, I purchased my 2019 NR tag in June and my 2020 NR tag in April. Thankfully, that was my last year to buy a NR tag.