Nope. No mystery at all.
Military people are taught to shoot nose to charging handle. If you shoot NTCH the critical part of the stock (as it applies t cheek weld) is the part just aft of the receiver, so that's where the cheek weld surface is needed. And where MagPul put it.
Assuming NTCH, if you are shooting so far back on the stock that your face is in that gap at the rear, you're head is to far back.
If you are using optics, and the eye relief pushes you that far back, you need to reconsider your optics placement, and move it further forward.
If on the other hand, you don't shoot NTCH, then the Crane or Vltor may work better for you, as the cheek weld surface moves further back as you extend the stock.