What's the possibility of Signal being removed? That's one of my most used apps
There are no public channels in Signal, so there's nothing objectionable for an app reviewer to see on first launch. Apple doesn't restrict any form of end-to-end crypto... except VPN apps in China. :-\
Correct. Telegram has public channels and groups, many of which are used to distribute porn. Earlier versions of Telegram for iOS prevented users from joining (and possibly even viewing?) these channels -- this feature was inadvertently lost in the "Telegram X" rewrite, which led to Apple's temporary removal of the app.