I mean that the bird blood recipe given doesn't cure leprosy
The Bible didn’t say it cures. you are not reading what is written. It says the concotion is applied AFTER the priest determinez the person is healed. It is used to make someone who is healed cermmonial clean. It is not how the person is cured.
Do you understand the idea of ‘foreshadowing’> the person in question is ALREADY HEALED, the ceremony is not to get healed.