If you see a scripted quest that allows minimum level 3 (as an example) characters to go on it, it is not true that the quest will be balanced for 3 level 3 characters. A better way to OOC'ly determine whether a quest is in the right ballpark for your group is to look at the max level - depending on what that max level is, you can generally assume that the quest will at least be somewhat challenging for characters of that max level.

The thing is, there are lots of challenging quests where we're okay with the idea of higher level characters involving a new PC by taking them on a quest. Generally the minimum cap is there because of other reasons - maybe the quest would be too rewarding for a low level PC, as an example, or for some other reason.

Anyway, I figure a lot of people have figured this out but I figured I'd mention it publicly.