In all honesty I had never considered using CA in a wood to wood joint like that before reading that writeup. That being said, if Kevin Ryan says its good I wouldn't hesitate for a moment to follow suit. As with any joint I imagine that the precision of the surfaces is key to having a strong, invisible glue line. Keep in mind, Ryan uses a veneer on both the front and back of the headstock.
I would also hesitate to consider the typical "ear joint" a truly structural one, especially when veneering both sides. I cant really imagine a significant stress on the joint unless you have a tuner hole right through the glue line. Look at most headstock ears out there. After all the machining is completed there usually isn't a ton of material even left. No more structural than a heel cap IMO. That's assuming a "typical" headstock size I suppose. Certainly not the rule though, I'm sure you could devise a scenario which would ask a lot of said joint if you tried. Like anything else its definitely an operation worthy of care and precision.
Just my opinion....