Ah okay, that' very different to Avid then. And in that case I see why Davinci would have to copy the render files. There are pros and cons to both ways.
I actually prefer the Avid way, where renders are connected to clips and are not deleted automatically. For sure, it kind of clogs up your HD but you just have to remember to delete them after a certain period of time. This could even get automated. This way you don't have to duplicate render files, you don't lose them when deactivating a track for example and you can always go back to a different version of let's say an effect for example.
Is there a way of not losing renders when temporarily deactivating a track? That's very annoying..
I am also just realising that moving the sequence content even only one frame deletes the cache. As much as I love Davinci's auto render cache functionality - I think there's still room for improvement