For many searches Google provides a short answer at the very top (like when typing 1 inch they show you 1 inch=2.54 cm). Does this count as a search result in Webmaster Tools under Average position? WMT constantly reports position 2 or 3 for some of my pages although they've ranked right below the G answer for months.
I can't give a definitive answer to this, but I believe it isn't counted as a ranking. I confess I don't use WMT ranking data very frequently for checking positions, but from a quick test I ran there Google's numbers were what I expected.