They don’t necessairly. There are hundreds of examples of clean-room reverse engineered decompilations, such as the ones that I have listed. The great part is that once it’s done for one game, that game will forever be open source and perfectly preserved, able to be relatively trivially ported to any platform from the present pr future, indefinetly.
I hate WhatsApp so much. I’ve tried multiple times to stop using it but it’s so ubiquitous (at least in Europe) that it’s impossible to live life without it. The only way this monopoly could be killed is EU government intervention.