Not endorsing Telegram but the only places I'm seeing the 'report' button are in group chats and channels.

I think a lot of this comes down to confusion by MSM outlets.

As I understand it, if Telegram permits you to continue the conversation from a different device, the chat is not E2E encrypted. This leaves me puzzled about the absence of the 'report' button in non-secret 1-to-1 chats. This probably won't be enough to appease the nanny state.