I would say i‘m experienced as well. All Extremes Gold, Inferno IV and Meteorain 10 faults, WOTM 6 faults, four national records on hard and medium tracks. But this Stadium Thing is too hard. And the very long loading times in the stadium kill the motivation to grind it. In other Tracks the loading at least seems way quicker.
I too read something about 18 Tracks in the Beta. And i unlocked the HongKong Harbor wirhout finishing the Stadium.