Its probably the same logic as Android. Google open sourced it, let many companies contribute and develop to speed up development to compete with iOS, then take it, thow a proprietary code in, close source and add google play without with most people cannot use it. 

So projects using the open source version will be beneficial, like AOSP based roms. Majority will get screwed somehow. 

 How do you back up the information that Signal was hacked? Tucker said someone saw his messages. I would guess thats some kind of OS tool like Pegasus. Havent seen anything confirming Signal was hacked.