They ensured that the citation request was not actually an additional requirement and has no legal meaning. Beyond that, GNU's interests are better served by retaining GNU Parallel as a GPL-licensed GNU product than by losing it to another organization or another license. I wouldn't expect movement from GNU beyond their existing acknowledgement that the citation request is not a legal requirement and does not modify the GPL. In any event, GNU tends to be hands-off on contributed packages (i.e. the ones that Stallman wasn't involved in writing).