You're implying that WhatsApp, Inc. gave the Egyptian government the ability to remotely retrigger this backdoor whenever they want to (for those who haven't actually read the article: this backdoor only works when WhatsApp issues a key change for a conversation, and only then in certain circumstances). In other words, you imply that Egypt said "Hey WhatsApp, please actively hack into your Egyptian users' messages and send us the results" and WhatsApp said "ok sure here ya go".
It might be true, but Zuckerberg might be a FSB informant and I might be Elvis reincarnate. These are all baseless, yet not entirely implausible claims.