The WhatsApp web portal requires Fingerprinting,
“Fingerprinting is a type of online tracking that’s more invasive than ordinary cookie-based tracking. A digital fingerprint is created when a company makes a unique profile of you based on your computer hardware, software, add-ons, and even preferences. Your settings like the screen you use, the fonts installed on your computer, and even your choice of a web browser can all be used to create a fingerprint.”
Therefore, Fingerprinting is not enabled in the Tor Browser.