This is an awful decision. I've converted some friends and family to Signal over the past years (it took a while) and it is now their default messaging app on their phones. This is going to confuse them and is going to make it difficult for me to keep convincing them that Signal is the route to use. ("Why do I need 3 apps (Android Messages, Signal, Whatsapp) to talk to people?")
Why three tho? Use one – Telegram.
Isn't Telegram partially closed source?
There is an unofficial FOSS version. I'm not sure if it is feature complete, secure, etc.