I usually try to leave the Magit praising to others in these threads but in this case I would have found it hard to resist. Glad others have already taken care of it. ;P
It probably doesn't make much of a difference because Magit's stashing commands offer more flexibility that even after this addition is still missing from `git stash`. Stash creation is actually one of the very few areas where Magit doesn't use the respective Git procelain commands at all (as opposed to using them and then doing additional things using other pluming and/or porcelain commands as is the case in many other areas).
Also I have to continue supporting older Git releases anyway; people like to use the latest Magit version without considering doing the same for Git, for some reason.
Will this change make your work on Magit easier?
If there was something you could add/remove to/from Git to make your life easier, what would it be?