Which species of Agave are known to have inedible flowers?

It is well documented that many species of Agave have edible flowers, however I keep coming across statements to the effect that “most species” of Agave have edible flowers. This implies that it is known that some do not, but I have been unable to find any specific references to species known to be inedible. I’m particularly curious about Octopus Agave (agave vilmoriniana), which I could find no confirmation either way, but would like to know any information & sources regarding the inedibility of any Agave species.