I think Google does the same with everything (email, web history, searches, ad profile, etc) but I believe their reasoning was that there is no way to guarantee

I think Google does the same with everything (email, web history, searches, ad profile, etc) but I believe their reasoning was that there is no way to guarantee that your data will be deleted from the backups, other redundant caches and whatnot, so they don't claim to be able to.