This is fake news...…..
Boneyard in Davis-Monthan AFB (or 309th Aerospace Maintenance and Regeneration Group) Only store aircraft that were operated (past tense) by the USAF for continue preservation and salvaging operation.
AH-1Z is a new helicopter, it would neither need continue preservation and salvaging done to it, which mean it have no point at all putting them with the 309.
If it was a commercial boneyard the article is on about, then that would mean those AH-1Z is scrapped as per ITAR act, which mean they are to be "recycled", which literally mean crushing them and remake the material into something else after taken out all the sensitive technology. Which again, being totally brand new aircraft, it's not likely it is going to be this way.
If and when US refuse delivery of AH-1Z, two things WILL happens, first, you are going to hear from it from the Pakistani and/or US government. Second, they will not be put in boneyard but rather induct them into US Marine, or sell them to third country.
So for me, this seems fake.