When traders "leg-out" of a position, they are not managing their trade as a whole. Instead, they manage multi-leg positions independently.
For example, instead of closing both legs of a strangle at the same time, a trader may only close one leg depending on the circumstances of the market.
Based on the study, managing our positions as a whole trade slightly performed better than legging-out. Plus, there were more opportunities to manage our positions as a whole compared to legging-out.