That's not true, because a very common way of getting a new idea is to start from something existing and then extend it. Thus a pretty standard task for any Ph

That's not true, because a very common way of getting a new idea is to start from something existing and then extend it. Thus a pretty standard task for any PhD student is to reproduce someone's published result as the first step towards testing the new idea. And even if you start by assuming some previous work is correct, frequently you will end up reproducing it in some what because you want to sanity check the extension you built on top of it.