This removed-sms-without-reason is going to be a myth that persists for a while
> RCS is coming, and it doesn’t play well with Signal.... and Signal can’t add RCS support because there’s no RCS API on Android. Honestly, the days of any third-party SMS app are numbered.
That reason might be a nice scapegoat that they invented after criticism because it's mentioned nowhere in their official announcement.
>There are three big reasons why we’re removing SMS support for the Android app now: prioritizing security and privacy, ensuring people aren’t hit with unexpected messaging bills, and creating a clear and intelligible user experience for anyone sending messages on Signal.
While this is true, RCS isn't here yet and when it is there likely will be APIs for it. The argument that there aren't APIs for a feature that isn't present isn't a valid one in my book.
>There are three big reasons why we’re removing SMS support for the Android app now: prioritizing security and privacy, ensuring people aren’t hit with unexpected messaging bills, and creating a clear and intelligible user experience for anyone sending messages on Signal.
https://signal.org/blog/sms-removal-android/
So I think this "myth" will probably persist for a while.