Probably he is referring to that WhatsApp is from a US company vs telegram with Russian origin.
general tendency in HN is Telegram bad, Signal/WhatsApp is good. Even small mistake made by Telegram will be judged harshly, when it comes to WhatsApp, their mistakes are not important.
Yes I am a Telegram fanboy (how can you not like such a beautiful/fast app, in the Electron world where everything takes 10s of seconds to load)
Signal seems like a pretty light/fast/good electron app (on windows at least)?
WhatsApp chats are end-to-end encrypted (even their iCloud backups are). Telegram group messages are always plaintext / available to Telegram, and Telegram 1:1 direct messages are plaintext by default.
Yet they hold the encryption keys to decrypt your chats on the fly. What inspires so much trust in Meta? Especially in a company with "targeted advertisements" as its business?