It's silly to try and touch the backboard... your hand will be leaning forward so it will be much lower than a full extension upwards...
If you want to measure something try a vertec.
Indeed , and here his hand has a huge angle , the difference with some frames before touching the board is obvious.
For freaks in the 50'' area , head height is more useful for calculating.
But for all of us caught in the mid/low/high 30's , highest touch is the way , so its really funny/nice to see someone like Darlington attempt a highest touch...