The way I see it, and I could be wrong.
The caps do four things.
1. For a semi-floater, they provide a pocket for the C-clip to reside in, so they don’t fall out.
2. They take the place of the removed center block which prevents the semi-floating axle from moving in.
3. For semi or full float, They keep the outer plates in place and keeps them from moving in. The caps fill the gap between the outer plates and the center pin and that’s where the feeler gauge comes in.
4. The caps act as a shaft for the inner plates to move side to side on as well as rotate on when the plates disengage while turning.
The spring pins can only align the two inner plates together. They can’t align the inner plates to the outer plates. And I think they are only meant to align the inner plates rotationaly because the inner plates could rotate separately from each other just a tad. That’s because the hole between the inner plates where the center pin goes, is not round and there’s a bit of slop right there. That out of round hole () is what makes the center pin drive the plates apart.
For a semi or full floater, without the caps, when the locker ratchets in a turn and the plates disengage, the inner plates could get off axis as there would be nothing to hold them on axis.
I really think the caps gotta be in there for a full floater. Just my thoughts and I'm always happy to be corrected.