Yes, I recently went through an upgrade from Calgary to Eureka at a client. I was given the arduous task of going through the upgrade log and deciphering if things were simply looked at and updated or if they were legitimately changed and needed to be avoided. If nothing had been changed, I reverted it back to original in an update set and promoted that through QA and Prod.
Then we cloned the dev instance with my applied update set, and re-ran the upgrade. It worked, and upgraded the various areas as it should.
So to clarify, if you look at something like an ACL, and click "update" or "save" and make no changes, that alone will let the upgrade skip that sys_id.
