A randomly generated quest will have to be level scaled because it can be generated at any level.
No, it does not have to be leveled. That logic you are trying to convey is way off. If we carry that logic through ,we could say that well since in theory I could go across the map at any level, everything I encounter has to be level scaled.
If it is a quest that you can pick up at any level, it does not mean it has to be scaled to that person's level. Maybe you'll just have to do something else before you are good enough to take it on, or maybe it will be really easy and you'll breeze through it. It should not always "designate opponents that are appropriately matched to your strengths and weaknesses" and give you a "challenging but fun" encounter. I want to come across a quest sometimes that punishes me until I cry tears of blood and give up, while other times I find a quest that is "challenging but fun", or even easy but NOT ALWAYS. Personally I would like to see these randomly generated quests to be just that, random. Including hardness. Not everything in the world and in life, especially the random events that spring up at you, are matched to your strengths and weaknesses.
Please god, let there be mods like there were in the other TES games. Out of the entire article, which overall I found really awe-inspiring and very good, THIS bit is what scares me the most.