That's primarily because it also supports sinultaneous USB OTG for some reason (likely Samsung's bizarre checkbox marketing team...) The GS2 supported MHL over the regular connector.
I hope companies start developing MHL compatible docks now that many high end Android devices are shipping with it. A good ecosystem of devices would prevent "improvements" like Samsung's from taking root. (obviously, Apple adopting it would have been enough to finally make one unified accessory ecosystem, but Apple can't charge exorbitant licensing fees for "Made for MHL" logos...)
It would seem that the 11-pin Samsung variant would have enough pins available for all of Apple's backwards compatibility needs. I too wish they'd gone in this direction instead.
I hope companies start developing MHL compatible docks now that many high end Android devices are shipping with it. A good ecosystem of devices would prevent "improvements" like Samsung's from taking root. (obviously, Apple adopting it would have been enough to finally make one unified accessory ecosystem, but Apple can't charge exorbitant licensing fees for "Made for MHL" logos...)