When the CIA funneled money to modernist artists, they weren't expecting spy devices in paintings. They're waging a cultural war.
Is signal funded to put backdoors? Maybe, but probably not. It's probably something more vague - A tool for anti-gov actors in countries that are our enemies, or to sell us all the idea that we are able to freely communicate while our devices are tapped by other means.
You replied to a "still, good to ask in order to seek clarity" type point.
Comment hierarchy is part of the overall context.
The root comment is a perfectly valid question. Since the government wanted to replace the guts with custom Motorola/Intel parts, it's a bit weird that they'd single-out NeXT to sell them an off-the-shelf shell. I'm guessing that Steve's number was in a lot of government Rolodexes after Michael Dell and the others.
He signed the visitor log as working for 'the company'. The CIA bit was a well-trod inference.