Which is to say WhatsApp is perfectly secure as long as the hostile actor cannot access the WhatsApp backups. Only nation state actors might be able to do that.
I think the threat model here is less about a hostile actor subverting the backups than the extreme ease of access to all data on those systems that is given to law enforcement?
Nah, all it takes is a good spear phishing campaign like the iCloud celebrity nudes leak a few years ago