There are two separate issues you are not distinguishing from each other. One issue is whether it is ok to get an exception made to a good rule, and the other is whether it is ok to challenge a bad rule. You can’t judge the situation and distinguish between the two cases, unless you are willing to actually evaluate the specific rule.
There used to be rules saying there had to be separate blood banks for black people and white people. It was eventually decided by the courts, after expert testimony, that this rule was not actually necessary and it was causing harm due to the lost opportunities for matching donors to recipients, and discriminating illegally.
Now there is a rule saying there have to be separate organ banks for adults and children, and it is claimed that this rule is also not actually necessary and causes harm due to the lost opportunities for matching donors to recipients, and discriminating illegally.
These situations are exactly parallel structurally. That doesn’t mean they must reach the same result, because the medical facts may be different enough to change the result, but there is just as much moral right to challenge the rule in court as there was to challenge the old rule about separate blood banks. Therefore it is unfair to criticize this lawsuit, unless you think it ought to be obvious that the current rule is best.