A 36-game sample is most definitely not "nothing".
During 90/91, Hull played 19 games without Oates, scoring a total of 18 goals. That's about 75 goals in 80 games.
With Oates, he played 61 games and scored 68 goals. That's about 89 goals in 80 games.
The difference is clearly there. And I believe it perfectly illustrates the extent by which you overestimate Oates and his impact on Hull's production.
Oates added about 15-20 goals a year. Even without him, it's reasonable to think Hull would have peaked at about 70 goals a year.