Cant give a pen if attacker shoots.

[Nij]

Law does not always required or is applicable to facts. Sometimes they are based on opinions and opinions are can be formed based on outcome. For example the exact same borderline tackle that is usually given as a yellow easily turns to a red if it breaks a leg.

Or another example is how game management is taught. Two players face off, team mates quickly separate them and you can usually manage the incident with a public bollocking. If it leads to a mass confrontation, usually you caution them both. Again decision is based on outcome but it is what is taught as best practice because it works in game control.

We can argue whether a particular contact is too much or whether an arm position was unnatural or whether the ball really was a millimetre inside the box.
But once it's decided that the ball was in the box and the arm position was not natural, the only possible decision is a penalty - he who plays on to keep match control has already lost it, but won't realise until they give a decision that conflicts with the previous one, because they weren't both in agreement with LOTG.