I don't think that list says what you think it does. Obviously, if more players are entering the draft earlier, they won't be around to take when they're older. That tells of the cultural shift toward one-and-done which we all know about. A better question would be, "Do younger players tend to perform better than those who come out of the draft when they're older?" Even that isn't a great question, because the obviously talented players are much less likely to stay in school for extra years with the cultural change. Guys who stay tend to do so to improve their stock, and since guys can sit out years straight out of high school and still be first-rounders nowadays, there's little incentive to stay in. In order to try to find data to address this draft, you'd have to control for general talent and hype and isolate age. You'd also have to decide beforehand if it's more important for a player to be better in general or better over the life of their first (or first and second) contract.
A rudimentary way to approach the topic would be to look at the more recent drafts and see which players have been the best and how old those players were when drafted. One can go to BBRef's page on the 2012 draft, for example, and sort if by win-shares earned.
https://www.basketball-reference.com.../NBA_2012.html
Doing so shows that four of the top 10 players in that draft were juniors or seniors, and three more declared in their second year of eligibility. In 2013, five or the top 10 players were 21 or older, three more forwent their first years of eligibility and only two were first-year entrants. In 2014, six of the top 10 were one-and-dones, along with three second-years and one upperclassman. 2015 has four upperclassmen, three second-year entrants and three first-year entrants.
I'm not going to go into every draft, but looking ahead, there's a good mix of guys of all ages who end up being the best players in the draft. I do think MVPs and superstars tend to skew young. As I said, uber talents tend to be known during their first year and don't have anything to gain by not entering the draft. This draft is likely to not be that different given who's at the top. We aren't debating who to take with the first pick. We shouldn't expect the team is going to draft a franchise player. So if the goal is for them to grab the best guy left in the draft by the time they pick, they're not going to be particularly more likely to find that in a teenager than they are in a guy who used up most of his NCAA eligibility.
Also, ignoring the role COVID played in scouting for the past two draft is odd. Without a pandemic, I have a strong feeling that Primo would not be a Spur right now.