Good caution, Cheddar. The FCRA does not regulate, in any manner, what accounts a CRA must report on a CR, or how long they must continue to include it. It only regulates how long they can continue to report a derog on an acccount thqt continues to be included within their CR.
Apparently, the CRAs have an unofficial policy of routine deletion of an account from your CR once it has been closed for over ten years, but I know of no prohibition of them deleting an account at any time, for any reason.
So your caution is well placed. It could be nothing more than their desire to delete accounts that are causing them constant headaches in hearing the back and forth bitching.