Uhh, guys, I know what Extremis is. Extremis is a friend of mine. That's no Extremis.
Honestly, I don't get how this is evidence of Extremis.
Stark only stored the undersheath
to the armor in his bones, not all
of the armor. He can remote control the armor (which floats itself to him via it's own repulsors), but other than ehnanced/extra organs to ease the strain or operating the armor, there's nothing extraordinary about it.