The wall mounted mailbox was introduced in Late Night expansion 
You need a mod to unlock it for building apartments.
And Distinguished bookshelf is a store item, i think. Correct me if im wrong.
This thread would disagree with your assertion that wall mounted mailboxes came out with Late Night. While they were in the stock apartment buildings the weren't available in buydebug to use in custom built apartment buildings. They are obviously Late Night items as they are for use in apartment buildings but they weren't always available in buydebug. Now they are. No mod needed to unlock them.
The Distinguished Bookcase is stock base game content. You can easily check this by looking in the storage tab and select the filter for base game content.
It makes sense when you think about it. I've noticed other things as well. New beds and other furniture items to show off their new blueprint feature. In fact the first place I noticed the new book shelf and the new bed and other stuff was while playing around with the blueprint rooms.
Think about it, if they made blueprints with all the existing furniture we're all already familiar with the rooms would look okay but by including new furniture to showcase their new blueprint feature those blueprint rooms have a more spiffy and polished look even if we can't put a finger on why. Some might look and think "Oh, nice re-colors" but in reality much of it is all new furniture.
