I don't buy that. The diopter focuses the reticle. Eye relief is eye relief, and a separate deallie. You've already got the stock collapsed all the way, and the scope mounted about 1 1/2" more to the rear than an average sized shooter would.
Diopter adjustment is a function of moving the ocular eyepiece forward or back from its original factory setting. You move it back if you are farsighted. You move it forward if you are nearsighted. This changes the diopter of the ocular eyepiece and corrects blurred crosshairs for those with vision issues.
It has absolutely nothing to do with eye relief of the scope, which is a totally different function.
So when I say I've run out of adjustment on the ocular eyepiece, I mean I have the ocular assembly turned so far to the rear (as I am farsighted) that the eyepiece is coming up against its mechanical stop before the crosshairs are in focus. I'm sending the scope back to Leupold to see if they can move the stop back further or adjust the eyepiece lenses to compensate.
Those who have noticed the scope position relative to the buttplate is not what a normal person would have are correct. Note, however, the buttplate is NOT collapsed. In fact, it remains in its factory position. It appears to be moved simply because the cheek piece has been reversed.
Why would I set the gun and scope up this way?
Because I have three fused vertebrae in my lower neck, and cannot physically crane my head forward. Those of you who can "get into" a stock don't know how lucky you are. I can no longer do it. My cheekweld is now further to the rear of the stock, and in order to maintain the same eye relief, the scope has to be moved further back. I assure you, the eye relief - for me - is set correctly on this gun. As you can imagine, this frustrates family and friends who try to shoot my guns. Most can't.
This picture clearly shows what I'm referring to. These are a couple of my Browning 1885 Single Shot High Walls, the top a 22-250 and the bottom a 223. Both have Leupold 6.5-20x scopes on them.
The receivers are aligned in the image. Notice the scope on the bottom rifle is much further to the rear. Notice the difference in bases to allow this. The top rifle has the old Browning/Burris bases (no longer made) while the bottom has a set of Leupold bases, but they have been reversed.
That difference in scope position shows how much my fused vertebrae have limited my forward neck movement.
As an aside, the bases and rings in the bottom image are only temporarily installed. They are designed for a tapered barrel and cannot be reversed without damaging the scope tube. I've loosely installed the rings simply to check the eye relief. I'm in the process of designing my own bases and when I get the time will mill them in my shop.
Oh, and another thing, because my cheekweld is further back on the stock, my eye is lower, because on a field stock the comb drops to the rear. The rings on the lower rifle as shorter to compensate for that as well. I went from high to low.
In fact, here is a pic of my Savage 93R17. It shows what I had to do to get it to fit me: reversed the scope base and installed a cheek riser (a modified riser from an HK SL-8 rifle) to move the scope as further to the rear than normal and raise my eye to the scope centerline.
This is one reason why I like the Ruger Precision Rifle. It is modular and adjustable. I can easily get it to fit my particular needs.