There's only one possibility for that: incorrect starting locations (too close to a gold mine), this will keep the regular gameplay with all standard units, just a bit flawed (and it won't be classified as melee).
In all other cases it's altered melee.
They're two different things, that's why there are also two different types for it.
You must have the correct type in order for a map to get approved (otherwise people would search for melee and find a map with different races, edited units or whatever).