You're trying to tell me that its simple to understand. I'll raise your simple and give you simpler.
The rule says "initial contact".
- The initial contact (after his feet) was the knee hitting the ground. Initial = First. He had clear possession of the ball.
- Then his hip touched the ground. That is the second contact. He still had clear possession of the ball
- Then his elbow touched the ground. That is the third contact. He still had clear possession of the ball
All of these impacts were with clear possession of the ball. He was only required to complete the initial act. He fulfilled that and more.
Now, I know that the NFL rule is different than everywhere else. But, ...
- if a DB had touched James when his knee was down, then it's a tackle
- If a DB had touched James when his hip was down, then its a tackle.
- If the DB had touched James when his elbow was down, then its a tackle.
Therefore, given that James would be considered down and tackled after the first, after the second and after the third impact with the ground, had a player touched him, he therefore far exceeded the requirement to possess the ball following the initial contact.
What part of that is hard to understand? It's so simple!