Timjnf,
There will undoubtedly be different opinions on this, but for me, it's doing as accurate a representation of of a real paint scheme as possible. If a modeler is building for scale competition for instance, it would of course need to depict a documented aircraft, but not necessarily one that did (in this context) exist in WW1.
While there isn't anything wrong with embellishing on history, or having fun with "what if", it's not what I strive to do. But that's just me. Many modelers are quite happy with just having a (what looks to them) a good looking paint scheme. And that's fine, what ever floats your boat, trips your trigger or blows your skirt up.
That being said, the choice of a scheme brings up other issues like having the skills, patience ( and sometimes money) to duplicate the scheme, and (for me) I prefer to have something easier to distinguish if I'm looking at the top or the bottom of the plane when it's flying.
