This is easily proven false by simply looking at professionals which either by necessity or regulation require a strict secure environment.
How common is it that the military use iphone apps for classified information or to interface with military equipment. Do operators in powerplants or other sensitive infrastructure use iphone apps as interface to their systems. When security is a primary objective then having it hooked up with a third-party that continuously collects information that you have no control over sounds as a very bad security recommendation, especially when it has a independent GPS, GSM, and network capability which bypass normal network security tools.
If signal crashes and a crash report is generated, who get access to it on a iphone? Who might get a potential memory dump with plaintext? If that party is apple I would strongly recommend that one is first okey with the idea that apple has access to the plaintext before using such app.
If your standard for operational security is the military, I have very bad news for you. Or good news, if your opsec goal is "be way better than the US Military" (that news is: you are already way better than the US Military).
The military obtains what security it has by attempting complete segregation and isolation; because it's the USG, the world's largest IT department, there are "public" and "private" networks, both clones of each other, both running the same insecure software. Both public and "secure" networks have been owned up comprehensively by malware in the past.
To get a sense of how bad the situation is, go look at the Common Criterial EAL vendor list, note which vendors have obtained EAL4 certification, and then compare to the security track records of those versions. That'll give you the spirit of the situation without requiring to you actually endure an EAL validation, which is something I have had the misfortune of participating in.
How common is it that the military use iphone apps for classified information or to interface with military equipment. Do operators in powerplants or other sensitive infrastructure use iphone apps as interface to their systems. When security is a primary objective then having it hooked up with a third-party that continuously collects information that you have no control over sounds as a very bad security recommendation, especially when it has a independent GPS, GSM, and network capability which bypass normal network security tools.
If signal crashes and a crash report is generated, who get access to it on a iphone? Who might get a potential memory dump with plaintext? If that party is apple I would strongly recommend that one is first okey with the idea that apple has access to the plaintext before using such app.