What does the tone have to do with anything?
What is that world of difference?
The fact remains that humans and Ferengi met and interacted.
The "tone" was that of humor in that the Roswell aliens were our three favorite Ferengi from the future.
The "world of difference" I am referring to is that no human in 1940 was out exploring the galaxy and reporting back to Earth about the aliens they met.
Humans and Ferengi met and interacted in 1947. Then there were several wars, one of which almost caused the destruction of the human race, and most records were lost. Fast-forward to 2150 and "first contact" with the nameless bunch of bald, large-eared aliens (who, I might add, were not the only aliens the NX-01 crew came upon in their travels who weren't named.) So none of these hostile or potentially hostile races were reported to Starfleet Command?