I've noticed this phenomenon a few times before: find a question that was posted 10 minutes ago, look at the questioner's profile. Last seen 20 minutes ago. Does updating last seen happen asynchronously with posting a question? How long might the lag be?
I'm reluctant to add this link, since the phenomenon is probably short lived, but I just noticed it there. Here are screen images as of this writing...
On the question:
In the profile, clicked a second later: