If you ask FL directly if they are selling the faulty dice, they say that they are but you can ask for replacements.
1.
Knowingly selling faulty goods is unethical even if you do other ethical things such as replacing them after.
2.
Im sorry, but what I see here is a parasocial relationship causing some to defend a minor but clearly unacceptable choice FL has made to reduce their costs.
3.
1. Out of curiosity, what was the actual question asked: e.g. "Are you deliberately selling faulty dice?" OR " "Are you aware that currently dice sets you are selling still have faulty dice in them?"
2. On this we simply disagree whether correcting a fault is sufficient to overcome a negative label. I think that if you fail an exam, and then pass that exam on a subsequent attempt, you deserve the credit.
3. I too am actually critical of FL, but would consider it possible that they are guilty of casual - or lazy if you prefer- management of this issue.
Since I do not know if FL are saying it is acceptable for them to dispense faulty Feat dice or not, I feel the choice of "unethical" is too damaging a label to apply here. Based on their actions, it is (as another post points out) more likely that there is zero cost reduction here, rather the opposite. They are covering replacement and postage costs. The speed FL have acted and their complete acceptance of the problem actually suggest to me that "Ethical" is a fairer label.
I also find your application of the phrase "parasocial" curious. I had a scientific training in my education, and I just need strong evidence to apply strong opinions. Jumping to conclusions about the motives for the actions of others is alien to that training. It may well be that FL are an unethical company, but this is insufficient evidence to conclude that. So far the evidence points in the exactly opposite direction.
(And I would hope to be just as parasocial in any other instance.)