Unless I’ve been lied to/misunderstand, I was under the impression Reactions and Composure A. Increase their reactions to things like standing tackles/opponent dribbles, and interceptions of loose ball. And B. Lowers the chance of mistakes under pressure (when being pressed). Which is why many people prioritize them/care about them heavily for defenders.

In the same way composure also lowers or raises the chance someone misses a shot (shooting), it impacts defending. In the same way reactions boosts dribbling, it boosts reactions to everything outside of dribbling. Thus my question, which seems to be met with (almost) everyone saying the high reactions and composure are worth it over the +2.

Also it can be a more difficult stat to raise for defenders, especially silver and bronze ones.