Earlier quoted context omitted.
Part of being an engineer is making products that act the way the users want them to act. The fact that a Telegram bot owner can see everything the bot does is not what most users want/expect, and is therefore an engineering deficiency. Obviously fixing this deficiency isn't easy...
If users want something functionally impossible then that’s an education thing not a product thing. I fully expect that when I send text to a service that the provider can read all of it. Like of course they can, they have to process it.
Or telegram themselves could run a "bot server", where bot owners could upload code to, but not inspect logs of messages going to/from each user.