Yeah that's true - people do tend to dualize themselves. As a pretty firm ESI, my wife is looking for me to be more of an LIE sometimes, and in a lot of ways I am for her. But I'm not really an LIE. When we first started dating though, I was totally more IPish and did need to learn to be a lot more proactive and take charge about things. Wasn't that hard, really.
As for the stats, what I thought was interesting was that 64% of people marry within their quadra. I think the 71% figure was when only looking at married couples from a particular quadra, 71% of the time they were duals. 45% of married couples are duals overall, and 64% marry within their quadra. Sounds pretty believable to me.