Interesting. Unless I'm missing it, the rules for storm shields were not updated in the FAQ, but they are updated in the FAQ for the new box.
So that implies that the storm shield rules leaked only applies to the primaris storm shields doesn't it? Or did I just miss it?
That's correct. From the Edge of Silence FAQ (the mini campaign book in the Indomitus box that contains the datasheets for the new units)
When used in isolation – say, when playing through the missions in Edge of Silence – these rules work perfectly well, but when used with a Battle-forged army, it is possible to upgrade a Character with Artificer Armour, and in doing so have a model with a Save characteristic of 1+. This was not our intention, and so we are changing the rules for both these items of wargear as they appear on these datasheets.
Please also note that while some weapons and other items of wargear (e.g. storm shields) appear in other places with slightly different rules, the rules for them that appear in Edge of Silence should not apply to other units – you should continue to use the rules as printed in your current Codex for the time being.
So any other existing stormshields keep their 3++ for now. It also means that the new 'astartes chainsword' only apply to Assault Intercessors, and only the bladeguard get master-crafted powerswords with +1S.