My take on it is like this…very much like what has already been said....
I have about 20 performances where I keep all the same slots with the same settings. This is a good candidate for locking all slots.
However, I have another 4 “special” performances where everything is completely different, for surf and rockabilly.
If I lock all the slots, I now have to unlock before selecting one of the “special” performances which is completely impractical on stage.
So, to avoid that I have all the 20 performances saved with the same settings.
OK, you might say, but if I decided that for example the reverb is too high (on all of these 20), I have to go through all 20 performances, edit them and re-save, which is quite a pain. So much so that I have given up refining these slots.
Globally locking all slots, then selectively picking a performance and being able to “withdraw” it from global locking would, I believe, eliminate the problem.
I’m sure this issue is not just mine and I've seen no other way around it in 7 years, unless of course I have missed something obvious.