Do you think the developers consciously made the decision that Nirn would have weaker gravity than Earth, or do you think they just messed up the physics?
Could be both. You never know.
Besides, Oblivion was Bethesda's first try with physics, so I can assume we're not going to be seeing slow falling bodies in relation to the gravity on Nirn, whether it be greater than, lesser than, or equal to Earth's.
I just thought I'd chime in on the concern of realism, because when it comes to realism on Nirn, you never know.