Lack of understanding basic english
Hailing something as "nearly impenetrable" has 2 major problems.
Firstly labelling something in this way you paint a huge target for people to prove you wrong and attract all the wrong kinda attention which you never want from a security point of view.
Secondly the phrase "nearly impenetrable" is complete bollocks, something is either impenetrable or it isn't. There's no nearly, almost or 90 %. It's like saying that as you have lived a reasonable period of time that you are almost immortal.
Also I am sure that others will have had the same thought about a ship named "Titanic" which was hailed to be perfect and unsinkable. For any that don't know the history the said ship on it's maiden voyage fell flat on it's arse and to this day remains on it's arse at the bottom of the sea.