You would have a point if the post author didn't also claim to be having the same success with Russian (also rated notoriously hard to master for english speakers). The tone of the article also implies that the same technique can be applied to any language.
That said, I still doubt actual fluency is obtainable for non-mavens even in the romance languages. In my experience, all early learners have a naive view of their own ability, no matter what the target language is.
He mentions right at the start it took longer with Russian.
RTFA.
The US Foreign Service Institute makes estimates for language difficulties for native English speakers, and they seem to be spot on in terms of comparative difficulty—Russian seems to be taking twice as long as French did for me, and they estimate languages like Chinese to take twice as long as Russian.
That said, I still doubt actual fluency is obtainable for non-mavens even in the romance languages. In my experience, all early learners have a naive view of their own ability, no matter what the target language is.