Assets, content, models are made, modelled in third party software like 3dsmax, maya, modo, etc before integration into any game engine.
Rendering these assets and showing and evaluating the design/texturing direction before integration into any game engine is how it's done.
Whether you do it with the integrated renderer in Modo, with a plugin renderer like Octane Render or Vray or Mental Ray, It's part of the visualisation and development stage of games and everything else.
There is nothing inappropriate taking place here.
It is how it is done in any industry where there is a design process.
Car manufacturers do it.
Architects do it.
Fashion designers do it.
Yacht designers do it.
Elon Musk does it
Explain to me and everyone else in the world how these practices are "completely inappropriate"