I don't mean that NDAs are bad in general, but in this case it's most likely just for the API or the signing process, because I highly doubt that they would create a mod-system that requires laying open relevant parts of the game source code.
I think it's more a preference of information clutter/processing than wanting a challenge. A lot of people have problems to concentrate on the main objective/information or lose immersion if there is too much text/stuff on the screen cluttering things while others have no problem ignoring that information/clutter until they actively seek info from it or have no problem processing it on the side.
And actual replays and maybe recordings on youtube are probably mostly done with vanilla WoWS because it's what everyone knows and all that information doesn't really matter for viewers at that point.