"watermarks" will still be there...
some make mountains flat, some don't use the "raise" tool, etc.

I think you misunderstood me. In this case, "watermarks" refer to indications of authorship in any of a map's resources.
For example:
People often write in scripts:
By Sozdatel, etc.
And we know who made the map...

closed test? how is that possible?

A closed test is a test conducted by a group of people (or even just one). Currently, no one else is allowed to receive the map except for these testers.

I think everyone should test the maps

Not quite: everyone can play, but only after the tested version, where there will be and should be fewer bugs.