Although it's a useful method to stretch alternative muscles, overall you end up wasting more energy by being out of the saddle. Unless you're racing someone and need a spurt of speed, I'd tend to stay in the saddle.
Agree with you with some observations.
As a generalization, it seems like out of saddle climbing favors shorter and powerful riders over taller and thinner riders. Quintana versus Froome for example.
From what I have seen on group rides and in spin class is that the shorter riders find it less awkward to be out of the saddle. Perhaps it's their shorter levers, like gymnasts do well with gymnastics. Heavier riders also seem to enjoy using their full weight on a pedal stroke to punch the pedal down compared to a lighter rider. (Perhaps heavier riders also want to give their rear ends a break too.)
In a spin class there was a short (under 5'6"), powerful, climber that could/did the entire hour without a saddle because there was a bike without one. He was doing it at various cadences while getting in a good workout. He's known to do well on hill climbs.
On the road, I've noticed the same pattern. At 6', I feel uncoordinated out of the saddle like a center in basketball trying to dribble and play like a guard. I do get out of the saddle occasionally while climbing to try to develop some skill and power; yet, for long periods my average speed is better if I stay seated. Since it seems this way, I've been working on being more comfortable and efficient while changing seated positions which trends me towards staying seated even longer.
Climbing out the saddle well is impressive if done well. I wish I could do it well as pictures of the pros climbing out of saddle are used more than pros sitting in the saddle while climbing. It's like the public thinks that those seated are not working as hard or too tired to get out of the saddle. On the other hand, using watts seems to have changed perception of climbing effort and practices among the pros.
In closing, I wish I could get it up more often in spin class with the ladies or on the road with my mates to impress everyone. However, it's so difficult that I usually stay seated as I age and lose coordination and power.