"When you argue with him, you make him feel that you are at the same level. Don’t!"
This is a great piece of advice when supervising a bullshitter. I have wasted time and energy whenever I have ignored it. Short, authoritative messaging works best.
Whatsapp on the web browser encourages to download the app, making disingenous claims that the app is faster and as if it is impossible to do such calls within the browser. Most probably the "app" is the same code that runs in a browser but wrapped within electron. And by being able to run outside of the browser's sandbox (being an app), it can access more of your system and gather more personal information.