Currently, my short action 7mm WSM is using a bolt head for the fixed ejector. Can not stand it!

I want to swap out the bolt head with another magnum face w/ the plunger style ejector. No big deal right? MidwayUSA lists the long action bolt heads with the magnum face as not being compatible with the short action receivers.

Why? Is it something to do with the fixed ejector, cause that can be removed quite easily.

TIA