This is the actual development:
File:10May 16May Battle of Belgium.PNG - Wikipedia
File:16May-21May Battle of Belgium.PNG - Wikipedia
Operational refers to a level of command involved in campaign level warfare.
When Hitler or any other German officer referred to "operations in the classic style", they mean maneuver warfare exclusively.
Operational level of command is a modern invention. However, for example, to the Germans you were not "operating" when you were dug in with static defense. Althought in modern interpretation you can "operate" even if you are just defending a static line (in fact, in modern sense, you pretty much have 'operational level' officers regardless of what you are doing and any defensive plan is an operation as well).