Not a bug. All missions work when maplist has these on the list. Simple reason: there is not just one person responsible for naming every single map throughout the evolution of PR. Underscores make some names more readable or more easy to differentiate from others.
I see what you mean but naming conventions could not follow "map_name" as not all maps have two words in the name, also "map" and "name" are not separate unique identifiers. The way to describe that sort of naming would be MapNameWord1_MapNameWord2, but wouldn't work for "route", right?