Well the 6+ is a Note4 sized device (slightly larger actually) which is a pretty niche market compared to the more reasonably sized phones like the normal 6. I don't really understand your point.
Where did you get that from? The iPhone 6+ is very tall for a 5.5" device, taller than the Note 4, but it's not as wide and a good bit thinner. Total device volume is 87.33cm^3 vs 102.55cm^3, so a significant amount smaller. That ties in nicely with the hands-on reports saying it doesn't feel that big for the screen size - thickness and width have a big effect on how a device feels in the hand.