As someone who has run extensively at both T&F and road National Masters Champs, and has been heavily involved in the Road Age-grading tables since 2015, let me make a few points.
1. The age grading tables are based on the best single-age performance, per sex, (world wide) at each distance. A smooth curve is then developed from the Open WR or WB to age 99. The curve is intended to mostly prevent age-grades >100%. A 100% AG is equal to the Open WR for a runner of that age. The 2020 age grade tables were developed by Alan Jones using my data and data from the Assoc. of Road Running Statisticians. So for example, Kipchoge's 2:01:39 =100% and a 100% AG for a 50 year old male = 2:31:07. In case you're, yes, super shoes had a huge impact on the 2020 tables.
2. Generally, good head-to-head competition, at least in the 800m - 10,000m distances, is rare at National Masters T&F champs. If you compare Masters ARs, you will often see Road times that are better than those on the track. In 2016, I set the M65 AR for 5000m at 17:44.03. (Ten days before the race, and 5 days before my 65th birthday, I ran a 17:17 5K on the road.) Three months later, I set the M65 5K Road record at 17:31 in Syracuse. at the same level of fitness. When I set the track mark, it was windy, and I had to continuously run around lapped older runners. In the road race, even though I ran the worst paced race of my life, I always had younger runners to chase. It's also important to remember, that there are prize purses at National Masters Road Champs (usually about $7000-$10000) with the best money allotted for the best age-grades. For National Masters T&F Champs, you get a medal and a patch.
3. If you compare the all-time top age-grades at the top four distances (5K, 10K, H Mar and Marathon) they are not that different. Due to the influence of super shoes, the 2020 age-grade standards got a lot tougher for the H Mar & Marathon and that accounts for much of the difference.