They were upfront about not being linguists, and said that their work needed a lot of checking. That said, yeah they apparently didn't do anything more than guess at meanings; and the talk of loanwords from Taino (Caribbean islands) and Mixtec (betonèd highlanders), which according to vlad have no reason to be in a Nahuatl text (the objections hold equally well for every language possibility, really, except Spanish, which probably have already been deciphered).

But so long as they're close to or indeed right about the plants illustrated being New World-ese, this is still a pretty huge breakthrough.