Well you know what opinions are like, and that was just my 2 cents. 3/8P cuts a smaller kerf than .325. The wider the kerf you cut, the more power you need. Now some may not agree with the "ruin" comment...and granted, that wasn't meant to be taken literally. But the whole point of the 241 (at least to me) is to be a fast, nimble, and light limber. I don't cut big wood with it. I have it for quick pruning and removing small trees. Others may not use it this way.
As for it being "designed" to run 3/8P...that's all I've ever seen them come with, and is the recommended setup by Stihl themselves. Maybe you could order it with .325, but no dealers by me ever stocked them that way. They were all 6T picco spurs.
.325 is to the 241 as full size 3/8 is to the 261. Cutting speed is not optimal, and you have to use a lighter hand. Much easier to keep the RPM up, and not stall the clutch with the respective smaller chain.
Having options is great. If you want to run .325, run .325. You may really like it. Run it and let us know what you think.