I have a single-handle (rotates 270 degrees) faucet in my tub/shower. I've noticed that it is always mixing in cold water, even when turned all the way to hot. I can prove this by holding the cold water supply copper with my hand and feeling it get colder as the water runs on the hottest setting.
According to this article: http://www.selfhelpandmore.com/plumbing/how-to-adjust-a-single-lever-shower-faucet.php, the 270 degree position should be hot water only.
I have read the instructions for my valve and the hot water stop is set such that it is not restricting the rotation of the handle in any way. There is no documented way to get hotter water out of the valve.
Also worth noting is that this is a brand new Grohe valve, replacing an old valve which had the exact same behavior as this one. Seems odd two valves would have the same problem if it were indeed a problem. Maybe it's just how pressure balancing cartridges behave?
The reason this is bothering me is because if not for this issue, I would be able to set my water heater's temperature lower. To get adequate heat out of the bath faucet, my kitchen sink is unpleasantly hot (kitchen sink always temps 10 degrees hotter than the bath faucet - it must not mix cold water in).