This is one of those cases where there are two hostas with the same name. One is registered and, therefore, the "official" version of H. 'Fortunei Robusta' while the other is a non-registered plants and needs to be renamed to avoid further confusion.

According to The Hostapedia by Mark Zilis (2009), this is "...not considered a legitimate cultivar name which has been used for at least two types of hostas..."

One of the plants known by the name 'Fortunei Robusta' is a green-leaved Fortunei-type with tall flower scapes  In 2005, Peter and Jean Ruh registered this plant as H. 'Robust Giant'.

Hosta Helper will call this plant 'Fortunei Robusta' (Ruh)

The other hosta sold under this name is a large H. 'Sieboldiana'-type plant. It was treated as a synonym for 'Elegan' by Schmid (1991). The name H. fortunei 'Robusta' was used by Georg Arends in 1905 for the plant that eventually became registered as H. 'Elegans' in 1987 on behalf of Arends.

Hosta Helper will call this plant 'Fortunei Robusta' (Arends)