@nodata: I think we have clearly established that you don't agree with Kovid, think that he is totally wrong, and don't like calibre's solution. Fine. You are entitled to your opinion. Kovid is entitled to his.
Why don't you move on from moaning about it, and instead fix it? Write the code for your 'rescan' button, ensure it doesn't break Windows or OS-X, provide the patch, and see what happens?