They manufactured it starting 1979 -- but they were ready by 1975. It was just politics.
The Japanese visited Járosi for the prototype many times and made a gazillion photos. There's zero doubt where the idea came from. As far as I am aware, Sony have officially recognized the idea came from Járosi and Járosi have acknowledged Sony's actual drive has improved on his.
The rigid floppy was invented in Hungary in 1973, patented in 1974 but only in Hungary and Sony have stolen the idea.