WhatsApp has no motivation to use SafetyNet. For one thing plenty of their users use cheap Chinese phones that aren't actually Google certified (but come with the Play Store anyway) and they know this full well from their analytics.

For another, SafetyNet is used primarily for DRM on streaming services and for banking or other financial apps. Absolutely no messenger uses it that I am aware of (unless you count Snapchat as a "messenger" but that's literally it).

Every FB owned app runs fine on Android devices that fail SafetyNet. No reason to believe that'll change because where's the benefit for FB?