In the picture Slide is comfortably sitting on the ground cross legged while his opponent is kneeling in a posture that is not comfortable. The board is on the ground, not on a table, not elevated at all. I'm 73 and can sit cross legged on the ground comfortably longer than you can kneel or stand looking down. Any time the arrangements of the board and player's positions is more comfortable for one than the other, one has an advantage.
Oxbridge students are used to that pose, if you know what I mean.

In the picture Slide is comfortably sitting on the ground cross legged while his opponent is kneeling in a posture that is not comfortable. The board is on the ground, not on a table, not elevated at all. I'm 73 and can sit cross legged on the ground comfortably longer than you can kneel or stand looking down. Any time the arrangements of the board and player's positions is more comfortable for one than the other, one has an advantage.