Is the following correct (I.e. it does not preserv free pages) and can be added?
You are hung up on the idea of free pages when this operation makes them irrelevant. Complete new files are written, populated to the extent of fill factor, then the old files are removed. At no point do empty pages get left over in the new file and they get treated the same as non-empty pages in the old file - they are utterly destroyed.
Sidenote how is the feeling about pointing to non-included extension?