You may have missed the point of this article. It is very probable that our Lord understood and spoke Greek and even Latin; we know he could read Hebrew. What the author is saying is that in everyday parlance, Jesus, His Mother, adoptive father and His disciples all spoke Aramaic.
We see this even today. Arabic has been adopted as the 'official' language of many countries in the Middle East, including Lebanon, where it is taught in the schools. However, outside the school and in the marketplace, the common language spoken is Lebanese - not Arabic. And even amongst the nations that have adopted Arabic as their official language, the form spoken is so different that an Egyptian cannot understand the Arabic spoken by an Iraqi.
Just like many of us cannot understand English as spoken in Texas :-)