Forget drawing the correct line or drawing one at all. I think the bumbling idiots at the PGMOL dictatorship are not competent enough to determine the correct instance the ball leaves the foot. And by that, I mean the last frame that shows the touch for the pass. I don’t think they’re doing that correctly either.
Think about this, if the review video is 60 fps (likely is 24 fps retrograde potato tech knowing the lot of them), if they use the instance that is 4 frames removed from the last instance of the touch of the ball, they are basically giving the attacker 4/60 = 1/15th of a second.
When you’re running fast, this type of margin can easily play you onside or offside. The margins are hairline thin. How easy it is for someone to make sure to use the exact frame that shows them onside regardless of if the ball is released at that very instant or later if they’re corrupt. Just think about it.
You are absolutely right that it is nigh on impossible to pinpoint the exact moment the ball is played.
In which case, isn’t it great that we have VAR? We can freeze it down to within a fraction of a second - beforehand we relied on the lineman potentially 50 yards away being able to look in two places at once.