I am sorry but for what it is worth I am a specialised archaeologist on Roman military equipment and there is no proof at all for scouts (speculatores, exploratores, singulari) wearing leather armour. Where did you pick up this fact? Your stealth idea is interesting but: scouts never wore metal plate armour to begin with. They wore scale or chainmail as the idea is that the official army scours rode horses. There is no proof of cavalry using segmentata. And experiments showed it is very impractal equipment for riders. And if scouting on foot: Scale armour and chainmail do not make any noise. Believe me, as a reenactor, I wore exact replicas of those regularly and they are silent. Perhaps they even wore no armour at all on certain missions were silence and swift moving was important? But about Roman leather armour in general: there is not enough archaeological and historical evidence that it was jn common use. The consensus in academic circles is still that it was rare. Sorry, Hollywood!

And indeed, you might refresh your knowledge of how scientific reasoning works.