Why do you think it is ignored? Feel free to suggest a way to improve the article, if you want :)
In my opinion this is partially addresses in the threat modelling section, where I mention the need to trust "The companies running the servers needed by the app to work".
Anyway I believe the threat you mention is a very difficult one to defend against, because probably even metadata alone is sufficient to construct a graph of relations. So, I maybe wrong, but if you do not want to trust any company at all, then even Signal may not be enough for you in this scenario. Regarding the choice of WhatsApp vs Telegram for this scenario, you simply have to decide if you trust more Facebook (which we already know supplies this kind of mass data to the US government) or the Telegram team. Or you can trust neither.
In my opinion this is partially addresses in the threat modelling section, where I mention the need to trust "The companies running the servers needed by the app to work".
Anyway I believe the threat you mention is a very difficult one to defend against, because probably even metadata alone is sufficient to construct a graph of relations. So, I maybe wrong, but if you do not want to trust any company at all, then even Signal may not be enough for you in this scenario. Regarding the choice of WhatsApp vs Telegram for this scenario, you simply have to decide if you trust more Facebook (which we already know supplies this kind of mass data to the US government) or the Telegram team. Or you can trust neither.