The player who knows the rules best may find the unfairness the rules accidentally permit.

Deep knowledge of the rules reveals where the rules fail. The person who understands the system best is best placed to find the gap the writers did not anticipate, which puts them at a fork: exploit it, or say it exists. Expertise creates that opportunity and does not settle what to do with it.

You will encounter your own version of this in any system you know well. When you spot a loophole, notice that finding it and using it are separate decisions. The most useful thing an expert can do is usually to report the gap rather than to work it, and that choice tends to define what kind of practitioner you become.