Disagree with this entirely. I had a whole thread years ago about my experience with this in F.

I had one incident in J on an A380. Woke up with 2 hours to landing and there was some bad turbulence. Wanted to open my shade to look outside and it was locked. As one of the FA was walking past I asked them why my blinds were locked and I wanted them unlocked. She said OK and left. 20 minutes later they were still locked, so I flagged down the same FA and told her I wanted my blinds unlocked. Again, nothing. 20 minutes later again I flag down another FA and told her I want to speak to the purser. The FA looked shocked and asked if she could help with anything. I told her that the blinds are locked, I requested an FA to unlock them multiple times, nothing has been done, and I want to find out from the purser if locking the blinds is standard procedure, and if so, why. The FA left to get the purser, but before she could the original FA came running up apologizing and the blinds were then unlocked. She asked why I wanted to speak to the purser, and I told her that I asked her multiple times to unlock the blinds and when it wasn't done I wanted to find out if this was standard practice to lock customers out from control of their blinds. She said no, not at all, they made an error and it should never have been locked. I left it at that, and this was the only time I had experienced it.