The right set of circumstances could come together as the flaps are deployed
1. in the middle of the turn, G is increased to tighten it up for unforeseen (but foreseeable) circumstances
2. extra drag from the G slows the plane
3. extra drag from the flaps slows the plane
4. pitching moment from the flaps slows the plane
5. crew is too distracted by #1 to act on the speed decay vis-a-vis power or trim, and too task saturated from everything. They only pull back more on the yoke to counteract the descending tendency, thus slowing the plane more
Planes have been stalled for stupider reasons than that, so I believe it.