I'm not sure if you're going to injure something with the shrugged grab. I would say no, but I have pretty strong shoulders, so that might make a big difference. Also, I honestly just like grabbing with 1 arm most of the time. I would say unless your shoulders are absurdly weak then it shouldn't really matter too much. To test this without trying it, just hang down from a ledge and let your arms "shrug" so that you have full extension in your shoulders. If this hurts, then it's probably not a good idea; if not, then by all means go for it.
The primary use for the shrug is in handstands and flipping motions. In handstands, shoulders pushed out like that upside down is the correct technique and will help in balance if you get it down correctly. As for flipping motions, full extension of the arms will get you the maximal height out of your flips.