I imagine it has more words than Russian due to the additional case (vocative). However, it’s only used in one situation, so I don’t know if that would meaningfully add anything to learn it for all the nouns. There’s also this post, where it states that:
We did this language by language. It’s always difficult to come up with some sort of multiplier for word requirements, but we did our best by looking at the number of unique words used in some of our basic LingQ-produced courses.