Yes. Arguably because of the organisational cost of maintaining both a web version (which they arguably need) and a native windows version (which they arguably don’t need).
Most of WhatsApp is UI veneer on a set of webservices. Unless they’ve architected their app badly, I’m not seeing the cost of maintaining a native software being substantial.
The issue is not that a native Windows app needs to run in a browser.
The issue is that a native Windows app has been replaced by yet another browser.