This is called confabulation. Heyerdahl actually DID sail a reed boat... the Ra... but it was sailed from Morocco almost to Barbados (The almost because they had to abandon the craft short of their destination when it was obvious it would sink before arrival).
It is really surprising, in this day and age of internet fact checking, that the author could not find this little tidbit and report it correctly.
More likely a case of not caring enough to look.