There is a difference between 'gusty conditions' and 'turning downwind'. Turning 'downwind' in a constant airmass with a fixed angle of bank is going to have the same performance impact as turning with the same angle of bank in a non-moving airmass. The ground track will, however, be different. Perception of groundtrack can cause a pilot to over-bank when turning downwind, causing problems. This is different from the mis-conception that you will 'lose airspeed turning downwind'.
Reminded me of the 1994 B52 crash due to nose drop in a steep turn.
https://www.youtube.com/watch?v=182AepOJjMs