[mbyron]

I agree that 8.4.1c is potentially confusing. Here it is:

8.4.1 SITUATION C: With R1 on third base, B2 hits a fair ground ball to F3 who
fields ball beyond first base. He throws to F2 attempting to retire R1. The throw
hits B2 who is running on the foul line. RULING: B2 has not interfered, since he
was running in the prescribed base path, the same as if he were advancing toward
any other base. Since no play is made on B2 at first base, 8-4-1g does not apply.
Had B2 intentionally made contact with the throw, the ball would be dead. B2
would be out and the umpire could call R1 out for B2’s interference. Otherwise,
R1 returns to third base on the interference call.

So, to the OP: this case is not what you want to quote to support your position about the lane lines. This case play denies "running lane interference" because the play is on R1, not B2 -- the ruling is NOT based on the fact that B2 is in the lane.

The case play also does not support the OP's "veterans": if B2 deliberately interferes with a thrown ball in this play, he will be guilty of garden variety INT, not running lane interference. Again, the position of his feet is irrelevant in that case.

The rules support you want is 8-4-1g(2), which states that "The batter runner is considered outside the running lane lines if either foot is outside either line." This provision entails that a runner stepping on the line is in the lane.