It actually is a bug because a dev replied back in 2017 that they are working on it. But in some games yes, this could be done to increase performance, but it still shouldn't remove textures, shadows etc. that You can still see.
Gonna post my suggestion here to not make a new topic.
Since now You will be able to lock vehicle parts to the vehicle I think You should also make them locked by default to the car wrecks meaning you need a Tire Iron to take the wheels off and a Wrench to take body parts off.
Is there any information when the years old shadow bug might be fixed?
I'm talking about the one when some shadows stop/start rendering depending on what direction you're looking.