I believe that is the point he was making. 90 foot balloons aren't exactly discrete and if they were ever used for spying, their shelf life would be extremely low with a high probability of ending up being seized by whoever you were spying on, on top of it. Maybe you have some self detonation mechanism on board, but now you also are sending something which could be perceived to be a weapon. It's just really not a logical concept, at all.

Most countries can't hit something hanging out at 60000 feet. The US can, but it can also blow up satellites.

So if you can send satellites over unmolested, maybe you also try with a huge-ass balloon. It's way cheaper. Worth a shot.