What he means by "I do not foresee any smartphone app ever being approved for this purpose." is that a commodity smart phone is an insecure platform, so the military will not be approving any app designed for a commodity smart phone.
And by insecure here, he and I mean that its not a platform designed and manufactured to meet the large number of requirements for handing classified information. It may be secure in the sense of industry standards or conventions, but its not secure in the sense of military information security.
And by insecure here, he and I mean that its not a platform designed and manufactured to meet the large number of requirements for handing classified information. It may be secure in the sense of industry standards or conventions, but its not secure in the sense of military information security.