One might think it does, but it doesn't make sense. If the spring is wound, it is still essentially fixed. So you are guaranteed a certain number of balance wheel oscillations & escapement steps for each full wind irrespective of how much load is on the entire mechanism. The watch will just run slower or faster delivering to completion those oscillations. As such, I'm gaining about 6 - 10 seconds per day with the chrono engaged (which is to be expected with the reduced balance wheel amplitude) which confirms my suspicions.
If I'm wrong, I'd be interested otherwise.