It's not just Uncertain which turns yellow if you are the PM or on the TL. There are several other yellow markers, such as add father, mother, spouse, children, and more.
A yellow marker is not a feature of Uncertain only. Each profile has a public view (no yellow) and a 'private' view that only the PM or TL can see, and includes yellow links that can only be clicked if you are the PM or on the TL.