FED 8-4-1g Interpretation

[mrm21711]

Question,

8-4-1g reads, in part: "A runner is out...if he runs outside the three-foot running lane while the ball is being fielded or thrown to first base."

My question revolves around the term "being fielded" included in this wording. What is this interpreted to mean? We know that the running lane and potential violations only relate to a ball being thrown to 1B. I notice the OBR reference, 6.05k, uses the term "fielded" as well.