As I understand it, the complainant may CHOOSE to request the court to levy statutory damages rather than actual damages at any point, but is not entitled to both actual AND statutory (17 U.S. Code ยง 504)
It also seems to be absolutely capped at 30K per infringement, not 50, and ranges up from $750. It also seems that if the "court finds, that such infringer was not aware and had no reason to believe that his or her acts constituted an infringement of copyright, the court in its discretion may reduce the award of statutory damages to a sum of not less than $200."
I think you are probably right that this specific function is copyrightable though, but taken overall, I think Microsoft's lawyers have probably concluded that they would win any challenge on this. Microsoft have lost court battles before though, so who knows?