Why does a segol change to a kamatz at the end of a pasuk (or on an esnachta), as in the word for bread in the last paragraph of the birkat hamazon? (I know that is the pattern. The question is why.)
This question seems different from the various questions on this change that have been asked before, such as: Etnachta on גֶשם vs. גָשם. The answer to that question leads to a dissertation that describes this change as "pausal lengthening" and describes that as "a normal prosodic effect" but does not give a reason for this change. I am seeking a reason rather than just descriptions of when it occurs.