WhatsApp's Twitter account made use of the uncomfortable nightclub girl meme to point out how Telegram users don't know the service is not end-to-end encrypted by default, which is indeed true. Telegram was unfazed, however, and responded by pointing out how WhatsApp's iCloud and Google Drive backups aren't end-to-end encrypted (it's in the works). This has reportedly caused WhatsApp chats to leak in the past.
— Telegram Messenger (@telegram) May 15, 2021
The third point, about WhatsApp being able to read chats because it can restore on a clean device isn't quite right — it's possible Telegram is thinking about account/metadata restoration instead. Even so, the first two points still stand up.
Telegram also took the opportunity to gloat about how its apps are open-source and support reproducible builds. It's been a couple of days since Telegram's burn and WhatsApp hasn't responded yet —unsurprising since it's impossible to refute these facts.