The website and the mobile app have different underlying code. The website is pretty ancient, and doesn’t reflect all the latest changes in the mobile app. My personal usage is to just use the app, because the website really feels like it’s old.
This post talks somewhat about the differences and is relatively recent.
That being said, there are some functionalities that only can be done on the website, such as updating example sentences. The app doesn’t have that capability yet.
But for general review, I think it’s just better to use the mobile app only.