I don't think changing the text is neccessary, or even user friendly.
This checkbox has the title "Select All" with default value set to uncheck, and all other checkboxes are uncheck (as in this case, I haven't test with changing group permission to see if they affect default checkboxes here, I guess they do), that's logically mean if all the options are not checked, it's state will be unchecked (because All are not Selected)
It's state will only be checked if, and only if, all the options are checked, hence the "Select All" title.
Put it in the context, if you only want less than half of all options checked, most of the times you will check them manually. Only when you want more than all the options checked, you will want to check it to select all first, then uncheck unneeded options.
Only when this checkbox is checked (means all other options are checked, too) uncheck it will uncheck all of them. Otherwise, it is in unchecked state, and check it will select all options.