The CIA has very good reasons for end-to-end encrypted messages to be widely used. You can't have agents in the field using custom apps just for themselves. You need them using a standard that lots of other people too to blend in.
One of the reasons why the US govt supports Tor too.
Your source is ridiculous: “In other words, Signal gifted the CIA “well over a billion” potential insurrectionists, by providing them with a means to organize their activities away from the prying eyes of local authorities.”
This is undeniably a good thing; freedom to revolt is a good thing.