Loose Ball Foul?

[MathReferee]

I was in a conversation with a coach following a game and he asked about the following situation. Basically, he is coaching a team that is not incredibly talented but they play hard from start to finish.

Situation: During a loose ball, A1 and B1 are running in straight paths. A1 dives for the loose ball, following his straight path, while B1 remains upright in his path. B1 trips over A1 and goes down to the floor.

The coaches complaint is that his player (A1 in the scenario) is often called for the foul and he feels they are being penalized for diving for the ball. If both players had remained upright and collided this would be a no call. My explanation was that in this situation it could be a possible no call if both players truly remain on their path and neither go into the other player's path.

I think the reality is that most of the time the foul will be called on A1 regardless, but why? What verbiage would you use to explain a blocking foul on A1 in this scenario?