Why is creating new folders during a smartsync not advised

Hi there,

I'm just curious as to why automatically creating new folders at the destination is not recommended during a smartsync?

I'm only using Smartsync to backup my drives, rather than a mirror, as to my knowledge it is the only way to use hashing of files and folders and guarantee that if I change the folder structure at the source, I won't need to completely re-upload everything again from scratch.

Have I understood this correctly?