I watched the TC interview with Durov (Telegram) and apart from it being a big Telegram ad what struck me is that he told a story about his employee being approached by "an intelligence agency" and asked to reveal information about what open-source libraries they use.
It is kind of strange since their apps are supposed to be open source, maybe he meant the backend? Nonetheless, it seems this has been their modus operandi for a long time.
Remember that NSA is openly interested in systemd and how it works. It's a double edged sword. They wanted to be sure that it's hardened as they like it, and note any "useful features" that might come handy later.
The thing is, as computers proliferate and we start to use them in more places, the effects of possible holes moves closer to our homes. From distant infra to near infra; from borderlines to our homes and transportation we use everyday. Even to our pockets via smartphones and other smart devices we host in our homes.
It is kind of strange since their apps are supposed to be open source, maybe he meant the backend? Nonetheless, it seems this has been their modus operandi for a long time.