I find this useful for an other purpose. It shows that defenses in the 80' and 90' weren't really better. TS as you can see was between .511 and .543 EFG% was max .498. last season TS was .542 and EFG was .498.
This just shows that defense may be different today but overal they are as good as the 80's and 90's defense when it comes to prevent effective scoring. Physicality is down, but the defensive schemes got more complex and effective (largly due to removing illegal defense rule).
Even though you can more clearly deduct this by avg Ortg of teams, and it shows the same picture.
If Handchecking etc. would still be allowed, most that say it is to soft now would complain about it, because we would see pretty bad shooting.
Also i don't know if it is possible to get decent data by position with a regression. Rules changed over the years, I assume that this has some influence on the Percentages (Handchecking makes it easier for Guards, no Illegal Defense makes it harder to operate out of the Post), on the other hand the Positions evolved with the rule changes, so maybe the influence on the percentage is small.