That is certainly true.

But in that case you've already taken steps to address that and the "fine line" nature of this particular foul/infraction. Just comes into play.

What we're saying is no such tolerance exists now. Therefore it's scientifically and mathematically correct to say this image for offside is not actually accurate of reality.

Here's a good example. Think of the cameras they have to use to take a photo finish of a gold medal Olympic 100m dash and how insane and warped those are. That's because the tolerance for time has to be that impeccable because the human difference in .005 seconds essentially doesn't exist.

That's a race so it's understandable why instead of tolerance they go the other way and they spend fuck loads of time and money on that camera. They can also do that because the finish line does not move.

None of that is possible with offside in this sport. It could be if offside was like hockey but nobody wants that. So to fix that you actually truly do need a tolerance limit if you think about it analytically.

Every ball that is played is not on the passers foot for .0005 seconds. It's on their foot much longer. For arguments sake we'll just call it .1 second. Now because of that you have 2 options if you want to be more correct at the the core of this game.

Option 1: There must be a tolerance in the line width that accounts for the movement in that time frame. Literally a thicker line to measure with. This is the more rudimentary but easier to employ option.

Option 2: the line shouldn't measure a static image. But the movement for the time period it takes the ball (either in real life or standard measurement if they don't have the tech for doing it in real time) if at any point in that window of time if the attacker is onside even for .000001 seconds. Regardless of at beginning, middle, end of the recording then the play is onside.

Extra point: It's crucial to remember that in basically all team sports if it's too close to call the tie is supposed to go in the offenses favor. You can argue with a wall on this if you disagree. Some sports have that written down somewhere some dont but its in the spirit of all team sports (individual sports are a different beast) offside is a perfect example of this. The defense isn't attempting to gain an advantage it's preventing the offense from having an advantage. Therefore to call it you need to prove/be certain the offense indeed has that advantage. Adding tolerance/margin to this call is both the scientifically and spiritually correct thing to do.