I watched the video and the robot most certainly did not grab the boy's index finger.
Sequence of events
1. The robot was capturing the boy's queen with a bishop. For that, it first removed the queen from the board.
2a. The robot next moved the bishop onto the square where the queen was previously located.
2b. At the same time, the boy prematurely moved his rook to the same square, he completed the move before the bishop has been placed on the square
3. The robot completed its final downward motion to place the bishop onto the square while the boy's fingers were still on the rook, thus pinning the index finger between the bishop and the rook
The robot didn't do anything it wasn't programmed to do