Update and Final:

With key on and rear washer energized and pumping, fluid was streaming from the upper right side rear compartment interior molding and the right side rear speaker cover.

Removed speaker cover and upper molding. Close examination showed rubber hose had separated from a plastic pipe union routed behind the speaker, before the hose snakes up to the roof and through the right side tailgate hinge to the nozzle. Reconnected the hose - plastic pipe union and tested; the rear washer-wiper is functioning normally now.

Suspect what happened is that the washer hose binded up in the tailgate hinge with repeated opening/closing, and the binding pulled the hose out from the plastic pipe union behind the speaker. Might have to apply some rubber lubricant at the hinge point; maybe that will lessen the rubber hose binding from tailgate action.

Thanks for the tips Klaus!