Rigoli's statement that "the companies were continuing discussion on the claims" leads me to rule out the USPTO action as the reason, as if the re-exam decision was the reason, why would the companies continue to discuss the claims.  Either they'd proceed on the course to trial, OR, they'd halt discussions pending the decision as presumably it would be a defining issue one way or the other (defining enough to warrant a stay).  Perhaps wanting to see what I see, but seems logical to me.