Interestingly there was a quote from Honda saying "Honda® invented the transverse inline-four motorcycle concept with the CB750K0" which was 3 years later. They do claim being inspired by a US maker Henderson who did inline 4's in around 1912 which again was trumped by the Belgians of all people with the FN of 1905 which raced quite seccesfuly even appearing in the IOM of 1908.
I think honda were over egging it just a bit.
https://hondanews.com/en-US/powerspo...e-four-history