When they changed our status to the "selected on hold" I was able to update my profile too.
So I don't think they need to change it to "under review" to allow us to update it.
Maybe they changed their mind and instead of selecting people strictly because of the date of interview they are reviewing the profiles and selecting people taking another kind of things into account. Some examples come to my mind: currency, total hours, performance in the assessment (skill showed in the sim, etc). It make sense that they need to take a while to "review" all the profiles, isn't it?
I remember some guy working at EK said in this thread long ago that they used this kind of parameters in the past.
I don't see the relation between the words: "under review" to "you can update your profile now".
Just a guess.