So have I and I disagree.I've have used both, both adjust quickly in reality and the difference in time is negligible.
Go take a rig with double adjustable arms and loosen the jam nuts on an arm and try to adjust it. You won't get much adjustment before they bind. The only time what you're suggesting would be an issue is if multiple arms loosened up enough to the point where they could adjust without binding. If that happens, you have worse problems and should probably stop working on your own vehicles.
Its a good point, and has been discussed in the past. But one thing that's not mention is that when using double adjustables, you now have 2 threaded ends. I personally am not worried about an arm "readjusting" itself if it gets loose, what I am worried about though is damage to the threaded ends if a jam nut does come loose, especially if aluminum is involved. Single adjustable arms are going to be stronger and only have one threaded end to worry about.
And if a jam nut came loose on a single adjustable arm, how long do you think the threads would last before they stripped out?