The Russian government spends huge amounts of money on developing DPI (deep packet inspection) technology, and, as the media reports, actively exchanges experience with the Chinese authorities. A semblance of the Great Chinese Firewall, the so-called Cheburnet, already exists. Most VPN protocols do not work in Russia, and in the event of any protests, they can completely turn off all communication services in a particular region, including Telegam, WhatsApp, Signal, and so on. Not to mention the already blocked Facebook, Twitter, Instagram, YouTube, and thousands of websites of local media. 

In the case of SimpleX, few people set up their own SMP servers, and by default, well-known ones like smp7.simplex.im are used. It is easy to block them using technical means. I think the essence of SimpleX's statements about privacy and anti-censorship is the lack of collection of any information about users.