I hope (and feel) like the ruse will not work.
WhatsApp and Instagram are much stronger brands, and are not already branded "Facebook WhatsApp" or "WhatsApp by Facebook".
That's not going to change.
Well, the splash screen says "Whatsapp from Facebook", and the description on the Google Play store starts with "WhatsApp from Facebook is a FREE messaging and video calling app."
So, it's out there, even if people haven't changed the way they think.
Disclosure: I worked for WhatsApp until 2019
Google is responsible for alphabets web services. Check out Wikipedia for actual examples like waymo (https://en.m.wikipedia.org/wiki/Alphabet_Inc.)
We still think of Alphabet as Google. So while Facebook may effectively become Meta, people will still say "Facebook does X" when they should technically mean "Meta does X".
By contrast, lots of ordinary people interact with WhatsApp and Instagram. It will be/feel different when they're "owned by Meta" vs. "owned by Facebook."
FB's rebrand seems targeted to everyday consumers, so I would bet their brand strategy would change to cater to that, in a way that Google/Alphabet never cared to.
The day facebook went down for some hours, she woke me up complaining "the internet was down"