This is another moment that's the result of me logically thinking mechanics through. If the watch's magic knows when to loosen things up based on it being able to detect snugness, then it should be easy to arrange a looseness that's just above the threshold of being too tight. If one were to try to make it looser than that, what parameters would one go by to tell the transformation when to automatically stop if it can no longer go by what the person had imagined?
Granted, the answer sounds like it should be pretty simple if Tedd can control percentage of growth at that point in the morph, but this is magic technology we're talking about. Who knows what complications Tedd's dealing with?