@Osaban: If there are still large discrepancies (are there?), make sure that you're running the reporting program UAC-elevated.
Thank you MrBrian, I'm aware of the UAC admin elevated status to run Treesize... The article you've linked on in your previous post specifically mentions that System32 is also a repository for "hard links" to winsxs which means that its size might be fictitious. I'm also aware that all these articles were written about 6 years ago when large hard drives were not the norm as nowadays, although for people using small solid state drives shrinking the volume of the OS might still be a valid strategy.