Oats

Question

I read in some modern sources that, although some Rishonim definitely wouldn't hold that oats is grain, the french word that Rashi uses to identify shibolet shual in the Mishna in Pesachim in fact refers to what we call oats today. Wouldn't this at least make oats a safek d'orayta? Plus, why don't we have to consider the accepted definition that all poskim have been using for a very long time? Can we prove that chita means what we call wheat?