Yes, thats the limitation. I doesn't allow 0 for that reason, but you can move actually everywhere.
The snap only jumps to the next grid if you are slow and close enough, this can be adjusted via the “Threshold” level in the defaults.xml file (which is 4 pixel if you didn't change it) if you are below snap is active. If you are moving fast i assume you don't want to snap, because a fast movement won't be precise and thus deactivating snap to suppress a “jumping” gadget.
The snap only jumps to the next grid if you are slow and close enough, this can be adjusted via the “Threshold” level in the defaults.xml file (which is 4 pixel if you didn't change it) if you are below snap is active. If you are moving fast i assume you don't want to snap, because a fast movement won't be precise and thus deactivating snap to suppress a “jumping” gadget.