Online gameplay. And finally an answer to my question, although not the one I wanted:
Ugh... You still have to sit through an ongoing race before you can play.
Around 4 minutes from selecting your kart combo to the actual start of a race.
Not so much of an issue initially, when we'll be playing marathon online sessions. But this will definitely be annoying later on, when you just want to jump on for a quick race or two, and have to sit through that every single time you go online.