There is a difference between a person and their account, and this policy serves to ensure that a person's userpage is not edited by another person. Sometimes IP edits to a userpage are actually done by the userpage's owner who simply did not log in. A seemingly legitimate edit made by an IP may be the userpage's owner and should not be undone, unless it appears to you that the IP was not the page's owner. Use your own discretion, in that regard.