But the ultimate point is if your primary evidence for suggesting that Adams is superior to Olynyk is Adams starts for a good team and Olynyk comes off the bench for an OK one, then you haven't convinced me. Especially if in the same breath you say Adams does "all the things you need your basic role playing center to do" and later on concede that advanced stats, at the absolute least, suggest Adams and Olynyk are closer than you think.
The ultimate point is that I think Steven Adams has demonstrated you can plug him into a good lineup and he can give you quality minutes and decent production at the center position, not unlike Timofey Mozgov (though I think Mozgov is better). There's a dearth of players who can do that, especially ones with the physical attributes to defend bigger guys inside and also move around on the perimeter and in the pick and roll.
Kelly Olynyk has not demonstrated that kind of fungible value. Not yet. But like you say, the advanced stats suggest the two are "closer than you think," i.e. KO has more value than your average third stringer on a mediocre team, like I already said.
Steven Adams is limited offensively, but he does what he does quite well. That's different than somebody like Thabo or Roberson, or a guy like Omer Asik or Festus Ezeli -- guys who at best fill their offensive role just well enough to not to kill their teams on that end of the floor.