Awful article that completely misrepresents the study.
Adderall doesn't replace caffeine sorry.
A basic Google search will tell you the mechanisms of action for these drugs are totally different.
A basic Google search will give you plenty of anecdotal experiences from people who actually use these drugs explaining that no they are different.
I use both, they are very different. Caffiene doesn't make me focus, it just makes me less drowsy. Adderall makes me focused and motivated. Caffiene cannot replace Adderall for me.