That's the point. You lose ownership rights to everything on the console and cannot redownload anything.
Formatting is meant only when you abandon the console
While it's true that formatting is meant for when you are "abandoning" the console, I am pretty sure your second "line" is wrong. If you go to support.nintendo.com and get to the formatting, they tell you to delete your Wii Shop Channel account first, before formatting the Wii. That leaves me to believe that the Wii Shop Channel info won't be touched (which makes sense since it is probably not stored on the Wii) and therefore if you had to reformat for another reason (some main file got corrupted some how, something that Nintendo didn't expect) you should still be able to redownload all your games that you purchased of the Wii Shop. All that you would lose would be any save files.