I've been looking / staring at the video for a bit, and I think they have a problem with dissapearing land tiles 
I tried to read all the messages that appear under the map... There are some places I couldn't decipher a letter or word. If someone has better eyes, feel free to correct me.
** Land tiles after Initial Land is generated **
Total land tiles: 3575
Bottom water Splat made ??? ( 0, 16) with a radius of 7.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Bottom of Map) **
Total land tiles: 3573
Top water Splat made ??? ( 1, 64) with a radius of 4.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Top of Map) **
Total land tiles: 3572
Bottom water Splat made ??? ( 2, 16) with a radius of 3.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Bottom of Map) **
Total land tiles: 3571
Top water Splat made ??? ( 3, 64) with a radius of 7.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Top of Map) **
Total land tiles: 3569
Bottom water Splat made ??? ( 4, 16) with a radius of 6.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Bottom of Map) **
Total land tiles: 3567
.....
Top water Splat made ??? ( 111, 64) with a radius of 2.
** Land tiles in MapGenerator::FillMarginwithwater - filled Horizontal Area with water (Top of Map) **
Total land tiles: 3070
Left water Splat made ??? ( 16, 0) with a radius of 2.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Left of Map) **
Total land tiles: 3070
Right water Splat made ??? ( 96, 2) with a radius of 7.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Right of Map) **
Total land tiles: 3070
Right water Splat made ??? ( 96, 3) with a radius of 6.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Right of Map) **
Total land tiles: 3070
Left water Splat made ??? ( 16, 4) with a radius of 4.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Left of Map) **
Total land tiles: 3070
Left water Splat made ??? ( 16, 5) with a radius of 7.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Left of Map) **
Total land tiles: 3070
.....
Left water Splat made ??? ( 16, 77) with a radius of 5.
** Land tiles in MapGenerator::FillMarginwithwater - filled Vertical Area with water (Left of Map) **
Total land tiles: 280? ( 6 or 8)
** Land Tiles after the margin is filled with water **
Total land tiles: 280? ( 6 or 8)
** Land Tiles after water is Blocked **
Total land tiles: 280? ( 6 or 8)
** Land Tiles after Mountains are Generated**
Total land tiles: 22?? (13 ??)
** Land Tiles after Cliffs and Coastal ??? Are Placed **
Total land tiles: 1879
** Land Tiles after map is Completely Generated **
Total land tiles: 18?3 (6 or 8)
NOTE: The extra tiles don't appear to be in MapData at this point.
Map Generation Complete
Creating terrain objects...
Terrain objects created.
Placing random goodie huts...
Placing random elemental shards...
Placing random resources...
**** Land Tiles after Temp map Data is Deleted (Cworld::Initializeworld) ****
Total land tiles: 18?3 (6 or 8)
**** Land Tiles After Game Initialization is Done (Cworld::InitializeGame) ****
Total land tiles: 18?3 (6 or 8)
Followed by what looks like compilation messages...
It seems they generate a huge piece of land after which they start cutting pieces out the (Top / Bottom and Left / Right) coast... I guess they have to work on this some more, because the resulting map has same large areas with very straight coastlines (where the original land mass already had some pieces cut out...).
Another thing we might be able to learn from this, it seems mountains / cliffs are not counted as Land Tiles in the engine. If this means mountains are unusable isn't sure off course...
