Begs the question, if a similar load-relief system is used on KC-10, then why not KC-46 already? Leaving it all to electrons?
Yes, that was basically the idea: the new fly-by-wire system that replaced the analog/mechanical flight control system was supposed to provide all the load relief/protection that the dedicated and separate hydraulic load relief system provided. The FBW system worked, but was not "robust enough" (whatever that means) to ultimately satisfy the Boeing engineers, so a dedicated and separate hydraulic load relief system was put back in. It's no big deal technically, but when all the margin in the schedule has been used up it becomes a huge deal politically and contractually.