Yeah, OK.
Oh, and 16 ohm = 8 ohm. I've never seen a pair test higher than a 7.3 (Can anyone else substantiate that?)
The output transformer/tubes of a fender quad/dual showman/twin are all wired for 4 ohms load total. It doesn't care what speaker combination. If you put too much resistance (load) or too little it can kill the tubes too soon. I find it hard to believe that a company like JBL with such an unapproachable reputation for perfection of production and engineering design would just say, yeah, whatever, we'll just wing the impedance tolerances.
Rick