I think you are falling for the “genius inventor” fallacy clueless normies love a lot.

People advertising signal everywhere look like those kind of normies to me too. Doesn’t mean much.

The reason it’s not known to be broken is that it’s not a high value target - most people don’t use “secret chats” in TG.

Fair assumption. But it means you accept most people are stupid enough to not want such a feature or smart enough to not need it. Telegram user base is reported to be 900 million though.