boot2v1 was the earliest version of boot2 commonly found on "insert startup disc" Wii consoles. It isn't very different from the normal boot2v2. Many early Wii games, including Wii Sports, came with boot2v2, so most people would have gotten that update with a game they played if it wasn’t already installed at the factory. We don't have much information about this, the only real knowledge most Wii hackers have is from HackMii.
The build date in this version of boot2 is August 13, 2006, the same time as IOS9v1. However, if this is the same version on the Wii Menu Uninstaller, then it is based on IOS9v256.