With a target like Snowden who is under constant surveillance and lives at the whim of his host country, he could expect that any off the shelf hardware he bought would be immediately compromised. His hosts would just make up some bullshit reason to part him from the device for several minutes and do an evil maid attack. Or from afar his hosts or another country's actors could exploit undisclosed vulnerabilities in his device's wifi or bluetooth layer that they have in their toolkit.

I agree I cover that in my OP.