That argument would not hold if someone knowledgeable is in the room as the same time[1]. Silence[2] would be the fork that actually does encrypted SMS and took it when Signal dropped it.

Why give away your SMS to a messaging app that purposely dropped their encryption to focus on online chat which is useless to me as I don't have a data plan?

[1]: https://whispersystems.org/blog/goodbye-encrypted-sms/ [2]: https://silence.im/