new uncured plugs, depending on what material its made of can raise your ph if you drop enough of them in your system at the same time.
from what I know other than not looking aged, there isn't any benefit unless you want live plugs (live rock).
In a medium to large water system even if a new plug was to release ph it wouldn't be enough to make a difference.
All that being said, of late I've been using plastic plug which don't release ph or need any special storage.