Thread creep but any decent HR manager should empty the application closet out after that time frame, including those interviewed already.
It places the onus on the individual as to whether they're in or out, updates the files of those that are in, cleans out the cobwebs of those that aren't and discovers new talent. Plus, it's free administration maintenance. HR placed an adequate time frame on it, one week is enough for anyone, if it's not you don't want the job enough.
I considered it a while back for a DEC job, no longer available so I've chosen to not update. I thought the email was appropriate and I'm grateful they gave me the opportunity to choose.
My suggestion to anyone looking at these positions (or any for that matter) do your homework, decide what is acceptable and if you take the position, STF up if you knew, or should have known, about certain terms that no longer appeal after you get in. You'll be a better person and operator for it if you do.
It's called 'taking ownership' for your decisions.