I do not know why the studs (shown on the right) are smaller in height. Im not sure on what studs these are for. I've always used the studs (shown on the left) in my builds with no issues. In knowing the stress involved with the girdle flexing under loads I am more confident in using the ones I normally install rather than the ones I pulled out of this engine I just received.
Last thing I want is for a main stud to over stretch or snap due to stress and so forth and have the crank work its way out and start dancing inside the block.