AIUI the breakaway connectors are needed because plastic mudguards aren't stiff enough to prevent buckling, so if a stick locks in there the whole mudguard can crumple up under the fork crown; metal guards OTOH should be stiff enough that they won't buckle, so don't need the safety releases.
I think that it's more about the breakaway connectors on the SKS guards. Could be misinterpreting that though.