Not quite, in 2018 they did add tracking protection to their list of goals for their Private browsing mode and have implemented features to reduce tracking/fingerprinting/etc while in it. The main focuses though were still the same at the start though: protecting against local data being saved.

https://wiki.mozilla.org/Private_Browsing

We target Private Browsing to 3 privacy goals; in a Private Browsing session, Firefox:

• Doesn’t save the browsing history or display it in the Firefox UI
• Prevents the session’s data from writing to persistent storage
• Protects the session’s data from online tracking