Getting bumped in a freight highsec should make the bumper flagged

That’s called inference.
People infer (because that’s how our brain works) rules from situations that repeat. It’s not about being good or bad to do so (it’s bad, but it’s the only way to enjoy a game).
The more exceptions you have to rules, the more annoying it becomes to follow the rules. To the point we move from game “depth” to game “cumbersomeness”. An example of that is the way Aura tells you to orbit the rats in the NPE. It’s stupid, but at the same time it’s needed to have a single rule to follow : orbit the rats to kill them.

It’s the same for concord. People don’t remember the list of items that actually create a suspect/criminal action. And the rule that they infer from Concord reaction if “if it reduces my mobility or harms my assets then it becomes criminal” . That’s why people don’t understand why killing mtu only gives suspect, but understand that festival launchers don’t. Even if they don’t formulate this, the brain process information to create the most generic rules.

So yes it’s not written in any rule of the game. Actually no rule is written for concord. When you start the game you can’t say in advance the real ruling. That’s why people make this general ruling. And from the general case, it’s “if you impend someone ability to act or harm his assets you get concordoken”.
The fact that bumping allows you to prevent someone from warping and does not produce a criminal flag like the point does, is thus absurd.

Of course we are all talking about modifying the concord rules, which means we KNOW they do not forbid bumping so far - otherwise we would not have asked for it. You must be particularly stupid to not understand this.