On Lionel Legacy, the database is in the base. Same when using the app, the database is still in the base. Minor difference, the app copies and syncs to the database in the base. Again, the CAB2 doesn't store the engine/accessory, train list database. It must talk to the base and what it displays is coming from the base.
This is why you can take your remote to say another track or club with a Legacy base- but all your stored info is missing when that remote connects to their base it displays the info from their base.
The app is slightly different in that to make it's displays and menus work, it too does store it's own copy but wants to sync that with the base. The base is master and the one that counts.