WhatsApp is tied to your phone number, not your Apple ID or iCloud account. So when you set up WhatsApp on a new iPhone (like the iPhone 16e you mentioned) with a different phone number, your iCloud backup won’t transfer your chats. That’s because WhatsApp sees the phone number as the unique identifier for your account — even if you’re using the same iCloud account.
If you want to switch to a new iPhone but keep the same phone number, then the chats stored in your iCloud backup will transfer just fine. But if the phone number changes, it’s treated like an entirely different WhatsApp account, and the old backup won’t be accessible.
This behavior is a WhatsApp restriction — not an iCloud or iPhone issue. iCloud just stores whatever backup WhatsApp creates, but WhatsApp decides how to associate backups with numbers.
If you’re changing numbers and want to keep your chat history, WhatsApp does offer a “Change Number” feature in the app settings. It lets you migrate your account (including chats) to a new number before setting up the new device. Let me know if you want help with that!