It sounds like it, although it looks like it’s a 6-digit pin instead from the image in the article.
There’s also this additional info directly from Facebook’s blog post about all this:
When your chats are upgraded, you will be prompted to set up a recovery method, such as a PIN, so you can restore your messages if you lose, change or add a device.
Is it going to be like Whatsapp end-to-end encryption where they just rolled out a 4-digit pincode for “backups” on their servers as the third end?
It sounds like it, although it looks like it’s a 6-digit pin instead from the image in the article.
There’s also this additional info directly from Facebook’s blog post about all this:
Is your issue that it’s 4 digits, or something else?
WhatsApp is using the Signal protocol for E2EE chats