Hmmmmm....what kind of math did you learn where a 22% increase in league scoring over a five year period ('77 to '82) is a "little bit".
You dishonestly picked the lowest scoring year from the mid-late 70s and matched it with the highest scoring year of the early-mid 80s. The eras averaged roughly 14% difference in scoring. Not an extremely small difference but not as substantial as you're trying to assess.
20 PPG scorers in '76/77, two players above 1.40.
63 PPG scorers in '81/82, nine players above 1.40
I would reduce the 63 to 54 to account for the 3 more teams in the league but then a league in transition always results in an increase in the elite scorers benefitting disproportionally. Regardless, it is clear there was a significant shift in the scoring levels of the league's elite scorers.
In 81/82 only 13 30+ year olds were 0.80 PPG or higher while In 76/77 12 guys were. The league just got better. A huge influx of new players and the first strong generation of Swedes and Americans. Hockey was still booming back then but the league didn't accommodate for this boom as in the previous era where the number of teams from 69/70 to 79/80 grew from 12 to 21.
Gretzky was already no1 in PPG at 18 competing against prime Dionne and Lafleur. Lemieux was 9th, Jagr was 101th, Crosby was 6th, McDavid was 3rd, Hull was 23rd, Gordie was 60th in a league of 150 people.
And yes I get it everybody matures differently, everyone has a different role on a team when freshly new etc. etc. but Gretzky wasn't that early of a bloomer as a teen unlike let's say Crosby or McDavid. 2 years later Gretzky's PPG went from 1.7 to 2.65.
So yep the league quality just got better.
You can come up with any number that fits your narrative if you "try to apply some sort of adjusting".
Using your method, Selanne was playing at a 152 point pace player in 98/99.
No he wasn't. Got anything better?