What's more baffling is the lack of design:

    "If you or the friend then taps the name of a song in
    your online Google account, it starts playing 
    immediately, rather than being added to the queue as
    you’d expect. A Google rep explained to me that you’re
    not supposed to tap a song to add it to the playlist;
    you have to use a tiny pop-up menu to add it."

Who thought that this possibly was a good idea or an acceptable way to release the product?

No, it's not OK to explain that you must use a popup menu to add it. It's plain fucked up. It means that someone, all too easily, can mess up the current playlist by tapping at a song. One little movement with your finger and you just ruined the mood by cutting the tune. You can't trust shit like this. People will be afraid to open up the playlist. This strikes me as just thrown together enough to work, but not designed to actually work well, in every sense of the word.