The reference for the 'stop' message to jit.movie reads:
"Stops movie playback. rate is unaffected)."
This is quite reasonable, and it would also be reasonable the other way round - that is, sending a 'rate' message shouldn't start or stop movie playback.
Unfortunately, when jit.movie receives a 'rate' message (different from its current rate), the movie starts playing. And since I have a float controlled by a pattrstorage setting the movie rate , every time I go to a new preset with a different rate, the movie starts playing automatically. The @autostart 0 attribute thus becomes ineffective.
Since I can't see any advantage to having a rate message start movie playback, I would consider this a bug. Not a big bug, but still irritating, maybe comparable to a flea.