As far back as I can remember, there have always been several covert bots from M$. One basically just grabbed images with a HEAD check first. One of the others nosed around on back pages that AFAIK never had incoming links. Could never figure them out. They were always around, so eventually I ignored them.
Lately I've seen one as you've described. I just figured it was collecting parental rating or browser security threat info for M$IE.