yor all wrong and right at the same time.
apple is forcing people to upgrade to 3.1 BECAUSE.... if you need to restore your device apple no longer signs the 3.0 software your required to upgrade to 3.1.
so while the OP's picture doesnt support his arguement as well as maybe proof that you can't restore to the 3.0 firmware or lower he is still right.
this of course i beleive is 3GS affected only.
you're right, IF he needed to restore then the only firmware he could get would be 3.1. but, from what I can see, the OP does not need to restore. he's trying to download an app. there is no forcing him to do anything. if he wants the app, then he'll need to update, but if he doesn't want to update, then he can't get the app. TOO BAD
the OP needs to learn that he can't always get everything his way. we have to make choices in our lives, so we should choose to make the ones that have the highest opportunity costs