I know Whatsapp is not big in the USA as in other countries.
However, could the developers develop a full-fledged Whatsapp app on the Portal?
The current half-baked web "integration" is not good at all. Regularly got signed out, no "Hey Portal" support, it seems like the smart zoom doesn't work on Whatsapp call either.

Most of the ads for Portal are for elderly users.
First, why would you make those targeted users sign up for Facebook to get started with Portal? Can't you learn from all of your collected data that may be most families prefer just want to stay on Whatsapp?
Second: those elderly users don't know how to point the phone and scan the QR code to sign in. Their child/ family members are not around all the time to help them all-the-time.
Third: why not support for "Hey Portal" ? Once again, it's not easy for them to reach for the screen and then tap on Whatsapp contact and then choose to make voice or video call.

Please please sit back, think of your 70 years old gramma have to get a smartphone, then sign up for a Facebook account (or the grandma have to open Whatsapp to scan QR code to log in) if that makes any sense to you.
Why not a native Whatsapp app on Portal, then let their child to log in one time and leave it be.