McBell
Unbound
Nope, that's exactly what the original gumball and box arguments do, they purposely conflate atheism with uncertainty, in other words they pretend atheism is what we call agnosticism, and that agnosticism is not a third position of great importance. All this just to avoid supporting a position, it's quite embarrassing.
The answer "I do not know" means nothing more than "I do not know".
The only way your "argument" works is to not only humpty dumpty the definitions of atheism and agnosticism, but to make "I do not know" mean something more than "I do not know".
You are trying to play a word game you are not very good at.