Vertical Freedom - try reading the thread instead of just the title. No-one is saying that VRS and autorotation are the same
AnFI - I'm not holding that paper up as definitive but highlighting that this is not a new issues and was investigated many years ago. However it is interesting to note the rates of descent are much lower in the old Brit document, due to the much lower disc loading (and power available) of those early helicopters. Modern aircraft have higher disc loadings and stronger downwash so the RoD required to catch up with that downwash is higher.