I was on an early up train on the Frankston line today (30 April), when no trains from the Caulfield lines were running through the Loop due to the signalling disruption. The announcement on my train was specific that NO trains were running from Richmond through the Loop. My understanding is, however, that trains on the Burnley lines were in fact running through the Loop as normal so I assume that the announcement was to avoid even more passengers than usual transferring from the Caulfield lines to the Burnley lines at Richmond.
While I can see the reasoning (if my assumption is correct), it seems a bit over the top to make an announcement that is incorrect. By all means, tell people, "There's an issue at Richmond, for Loop trains please transfer at Flinders St". But to go further and to state that there were no Loop trains when this was not correct just damages Metro's credibility, as inevitably people will find out the truth (as I did as soon as I got to work).
EDIT: In fairness, I see the information given at at least one station did say to change at Richmond (see Daniel Bowen's blog - http://www.danielbowen.com/2014/04/30/trainageddon-what-can-be-done/
). However, there was no information at the station I travelled from and the first I knew of the whole issue was when the driver's announcement was made.