They might be trying to express that the Matrix protocol makes it easier for Israel to spy on someone using it. That idea came up somewhat often about 2 years ago, but I don't know many relevant facts. It's also common for people to say that the CIA and Israel cooperate, so that might be the connection to the CIA.

The initial project was created inside Amdocs

In early 2000, federal agencies conducted a counterintelligence investigation to determine if Amdocs was being used by Israel to eavesdrop on U.S. government communications. The investigation found no evidence of such activity.

As for Signal, I am greatly annoyed that Signal requires your phone number for registration. Some people justify the centralization of Signal by saying that using a centralized network means that everyone using the network is using the same (good) security practices, and I've been told that the developers for Signal periodically express that they're trying to remove that requirement, but I still try to avoid using Signal (or any networks that I can't access without involving a phone number). The lack of progress on removing the requirement of your phone number from Signal (and the lack of information on where any centralized infrastructure is located) invites ideas about conspiring with the CIA.

Despite any uncertainty or discomfort, I defer to https://www.privacyguides.org/en/real-time-communication/ and https://soatok.blog/2024/07/31/what-does-it-mean-to-be-a-signal-competitor/ to determine what methods of communication might be suitable for me to use.