The old guys DO know something that you younggins do not know. Our eyes are fer shit!!
The ocular part of a scope is to focus the reticle for your eyes. That is the only thing that it does. As our vision fades we need much more adjustment.
I am 70 years old. Any scope needs to be screwed almost all the way back for my eyes. I automatically go all the way back/out,then just a couple turns in. This gets it pretty close.
The downside to this is that it takes away some of the much needed eye relief used for some heavy recoiling guns.
The scopes third turrett is for focus/parallax adjustment. The AO (adjustable objective) at the objective end of some scopes do the same thing. If a scope has neither,they are usually set parallax free at 100yds. --- SAWMAN