@fcwilt (warning: ramble incoming) My printer is an own-design foldable bedslinger so has a few frame and component quirks compared to commercial units. It was foldable because at the time I was a student and moved around a fair bit. Having a printer I could fold down and pick up by the handle like a suitcase was very handy.
I designed and built it back in 2015 when having a screw on one Z carriage and an end stop positioned below it was the "way it was done". I did not want to reprint and reassemble the rightmost Z carriage with its own screw especially as I am not a huge fan of having 2 adjustment points for Z: Z carriage offset and bed height. If the Z carriages are at the same and correct height (and thus X is perpendicular to Z) then the bed can be trammed to that without issue. To my mind it's more important that Z and X be perpendicular then bed trammed in accordance than adjusting Z to match the bed.
So having decided I do not like the Z end stop screw adjustment method (and given the fact that due to some long-forgotten design decisions I have 2x end stop mounts but not 2x end stop screw mounts) it made sense to remove the screw, glue on a pair of buffers to the Z carriages and mount the second end stop. 10 minutes design, 30 minutes print, 30 minutes gluing, soldering, crimping and plugging.
At some point I may take the time to go through the entire build and redesign it to smooth out any issues I've encountered in the past 4-5 years but this was a simple and cheap improvement.