That's against the LOTG thought. The LOTG talk about being 'closer to the opponent's goal line'. You can't get closer than on it. Your proposal is completely throwing out that wording and inserting your own.
I also don't see the logic from a positioning perspective - why is positioning on one considered different to the other? The reason the deflection counts off one and not the other is specific LOTG text, which we don't have here. So we look at precedent and common sense.
And considering the players 'on the line' is the only thing that works. Otherwise, consider this scenario:
An attacker and 2 defenders are all sprinting for the ball as it approaches the goal line, and it's a wet day. Attacker is behind the defenders. One defender stops it just inside the goal line, oversteps the ball, gets tangled up with the other, and they both slide some 5 yards past the goal line. The attacker stops 1 yard past the goal line. Another attacker behind touches the ball again to stop it moving, then leaves the ball for the first attacker to run back and collect as he runs into the goalmouth.
2 defenders are clearly 'in front of' the attacker, yet if we're putting them on the goal line and not the attacker, that would make the attacker in an offside position. Which makes no sense.
Not to mention that given the IFK is supposed to be given at the player's location at the time of the touch, it would be impossible here.
So that's why I think applying the same for the attacker is the only option that makes logical sense.