I don't follow. How is security equal to anonymity? If anything, security is what enables privacy, which could enable anonymity. There are plenty of circumstances where you need security, but not anonymity - for example a message to your partner. Of course if you do need anonymity, there's a lot more involved than simply installing a "secure app" or anything of that sort.
> Tying your identity to a phone number that can only be obtained by handing a telecom your government identity documents fails.
I don't know about that in the US. I was able to open a pre-paid T-Mobile account to use with my LineageOS Android device without identity verification. Perhaps it is different elsewhere now?
> And I don't know if anyone else has mentioned this, but uploading entire contact lists should also not be considered a natural feature of a secure mobile messenger.
That sounds troubling, is it what Signal does? Would like to read more about that - is there a Github issue for reference?