John in NM
If the thrust plate were tied to those tracks and the whole thing were a bunch beefier, that would distribute the clamping force over the area occupied by the tracks. If the plate were just bolted to the bench inside that trough, you've just moved your endgrain bolt problem from a place where it's easy to fix to one where it is less so - though admittedly the bolt heads will not offend the eye in there.

Given the length of the end cap, I don't think that's the problem with this design, the screws holding the vise bushing to the cap will pull out long before a bolt into end grain a foot away will. A better solution would be to put that bushing on the inside of the cap, then all the force is borne by the cap mounting bolts and joinery. But that presents a problem for the manufacturer - how to deal with different thickness caps? I think I would make an inside plate too and put bolts all the way through the cap, pinching it between the plate and the bushing.