By preselected he means it will be the active field. So you can "start typing" - type "Han" and "Hannah" will pop up. You just don't have to manually click on, or tab to the contact field.
Also, please realize this is just a concept and further research will be put into the it if it goes into development. A swift workflow is the biggest goal.
I think using email to shoot off "quick questions" (such as the message depicted on the page) to people is an abuse of the medium - that's what Twitter and iChat are for.
Often it's a sentence fragment, such as "Can you," followed by a continuation of the sentence in the body.