They may have “different legal entities” but it’s the same.
https://en.wikipedia.org/wiki/Yamaha_Corporation
https://en.wikipedia.org/wiki/Yamaha_Motor_Company
It even says in your link "The former motorcycle division was established in 1955 as Yamaha Motor Co., Ltd., which started as an affiliated company but has been spun-off as its own independent company. "
They may have “different legal entities” but it’s the same.
https://en.wikipedia.org/wiki/Yamaha_Corporation