Seeing that WhatsApp is using the signal protocol and encrypts all communications by default, I contest the notion that Telegram with its home-grown protocol and clear text by default is a step up.
All this is full of false negatives and positives, but concerns too much to ignore, if you’re after secrecy that puts your welfare at stake. If you just hide your pics from a corporate big brother, I admit that whatsapp and regular tg chats may have different weights on scales.
WA used to steal your contacts by default to improve Facebook's data set and probably still does.
The Telegram guy however left his country because he didn't want to cooperate with such entities (like the Kremlin which for me is kind of another organization that seeks to harm your privacy among other goals and is therefor comparable to FB and other spy-companies).