To be fair, the popularity of Faceless Void and Skywrath came out of nowhere. A month ago, they were considered trash tier heroes and nobody in their right mind would ever run Void mid. I'm really hoping that these teams have some secret team compositions that they are holding onto for the finals, for these preliminary matches, they are playing it super safe.
If you want to see stagnant meta, look at League of Legends:
League of Legends: 36 matches played, 40 champions picked
DotA day 1 group stage: 36 matches played, 76 heroes picked