I've got limited experience driving a lean burn Honda, but yes, that sounds like it.
Opening the throttle more is one of the reasons lean-burn is efficient: it also reduces pumping losses.
If you search around, you'll be able to find instructions on how to hook up a digital multimeter so you KNOW for sure when you're in lean burn, because you
really, really want to be in lean burn.
The fuel economy is amazing.
Going to get an MPGuino?? That's another, more useful way to tell when you're in lean burn mode.