I wouldn't say more proven but I totally get your point.
Part of the problem is that besides Gavaskar and outside of the black and white era English openers, there's a paucity of options for the openers slot. And let's be honest, none of them were as stylish or attacking as he was.
Procter has Imran and Hadlee as completion for the no. 8 spot, many push his former teammate's son as well, and Akram can also fill that role. Plus not everyone sees the necessity of having a bowling all rounder, while openers are a must.
But yes, he was also a beast.
Procter is unique, all other Bowling Allrounders lack something that stops them from becoming perfect bowling allrounders.
Hadlee - Batting not strong enough
Imran - Batting ( bar last few years ) and fielding
Kapil - Bowling below ATG level
Botham - same as above
Miller - Same as above
Pollock and Davidson a league below the above group.
Procter had everything, except big stage opportunities.
Barry Richards being opener might have some influence, but there are Sunny, Hobbs, Hutton, WG and Trumper.. Along with the likes of Sutcliffe, Sehwag.. Etc . So, I dont see scarcity of quality openers.
I think, its Sobers. His existence cancels need of Procters and Hadlees, just like Bradman at number 3, but then there are people who selects Viv in AT11 and plays him at 4 or 5.