Yes. an extended flex-neck, ratcheting end wrench is exactly what is needed.
I jacked up and blocked the car and put some good light on the subject which allowed me to come up with a plan to access those upper bolts. This is what I did:
1) There are two metal water/mud deflectors, one on each end of the bumper, mounted on the frame to, I assume, protect the backup light assemblies. When I crawled under the car the other day with just a flashlight to start removing the bumper, it appeared those were extensions of the frame and thus blocking access to the upper and lower bolts. With better light, it was obvious they could easily be removed. I removed those (EASY).
2) removing the shields gave me the access needed to remove the backup lights (which are mounted into the bumper) and which definitely block access to the upper bolts. I removed the backup light assemblies (EASY).
3) Steps 1 and 2 gave me more room to access the upper bolt, but no amount of fiddling and maneuvering would let me fit a ratchet or breaker bar and 11/16 socket on to the nut. An 11/16 end wrench does fit....but...the throw is short and there is little room to fit your hand in there to apply force to the wrench. I ended up using a ratcheting end wrench, like those you display, but which was was rigid, but curved. It too, was too short and it took an hour to work both upper bolts off. applying WD-40 liberally and working the nuts on and off (TIME CONSUMING AND MODERATELY DIFFICULT). The lower bolts and the middle bolt (behind license plate/fuel neck access) were EASY and were removed in minutes. Both wrists are scarred from shoving against the too short tool against the sharp metal of the back quarter panels. An extra long (15 inch or so) tool would have been ideal and would have made life a lot easier. I will have one when I reassemble the car!
