Hardly surprising, I mean telegram is not e2e encrypted by default and the companycan read all messages, most users don't know that they would have to use the "secret chat" to get e2e encryption, and still it uses a custom and rather exotic protocol that I don't doubt has some nasty surprises hidden in it. For privacy the Signal protocol is the gold standard currently, people should use that instead, or go straight to decentralized solutions like SimpleX.