This is a slightly weird one. On my Forerunner 165 (linked to a Pixel 8) whatsapp calls do not vibrate my watch.
Interestingly though, I'll get a single buzz when the call starts and a single buzz when the call is missed, so it seems like Garmin treats this type of notification not as a call but as a more standard notification.
The configuration I use on my phone has not changed since switching from a Fitbit, so having my phone on silent does not affect the ability of a smartwatch to receive a call event from the phone itself, it just seems like Garmin treats it differently to Fitbit.
Is there a setting I'm missing somewhere? The notification settings in Garmin for whatsapp are all enabled, as are the notifications on my phone itself.
Normal calls do work just fine though, it's only whatsapp as far as I can tell.