No, it's industry standard to advertise the total internal storage, not the free storage that's available to the user -- and yes, this is the case even for iPhones. Some devices have more bloatware than others, so it's worth doing a little research before you decide on one.
And no one ever advertises that you can expand your storage for app installation with SD cards, unless it's a Marshmallow device that supports Adoptable Storage (and LG, along with Samsung, decided not to implement this feature).
In nougat you won't get the option to move apps in the apps menu. To move apps you go to your settings menu and choose general then choose storage. When in the storage menu choose apps now you can scroll through your apps. Pick a random app. The apps you can move will say where the app is stored by default, tap that and you will be able to move your app to sd. For apps that don't support bring moved they just won't have that option. You have to go through all your apps manually to find out which can be moved and to move them.