I spoke to Nick about the same thing, and they are two completely different beasts. The ABS and TC included in the tenere probably doesn't help.
Honestly, spend the money on the flash, it changes the bike, and makes it rideable and enjoyable.
That said, my tenere is great with the clutch switch on.
One of the Tenere forum inmates offers a good flash for it as well ($125)
It isn't a true 15HP but it does make a big difference. For some reason there is a different map in use with the clutch lever pulled in. It is for testing of certain functions of the bike. That is all I know for sure.
The other less likely option is that Yamaha knew we weren't dumb and wanted up to have some fun for cheap???