But regardless of that point, your other argument feels to me like a discussion against the problems of mono-culture: we should all endeavor to have diversity of implementation, if possible. The more we can work towards federated standards and the ability to quickly pivot when someone loses our trust, the more capable we are of defeating attempts to undermine that trust. If we only have 1 implementation of signal and everyone uses it, then all an "evil" party has to do is find flaws in that 1 implementation. If we have 2 implementations, then some users are protected. If we have 1,000 implementations, and they all inter-communicate, then we have some hope that only some users are affected by each compromise. I'm digging matrix.org as a federated protocol, and I'm hoping that it takes root because it has many clients; an open, federated protocol; and the ability for me to run my own server.
I would advocate that even though we're relatively mono-culture on linux, supporting it at least gives linux access to the source code which would allow other implementations (anyone else keeping a close eye on Redox [1]? I know I am!). Support open protocols! Support federated protocols! I'll advocate that signal is a great, easy-to-use system for secure communication, and that the ideas of Signal are percolating elsewhere (see "olm" [2] the implementation of Signal's crypto protocol for matrix). But I would like to see stabilization in Signal leading to federation.