I would argue that it's almost impossible to start first with the mobile version so this situation should never happen. The computer version is essential for setting up and getting decks. The web version remains free as well.

Why would it be the case?

Anki app has an interface for adding/editing cards, and can absolutely be used without AnkiWeb or syncing. In fact, this is how I used it myself for years. I would argue that using AnkiWeb and syncing is an advanced feature for people who got the taste of having own decks and don't want to loose it.