It looks more like a genetic deformity. Unless the fish can't eat because it's too slow to compete with the other fish, it should survive with no extra issues. Sadly, fish farms are not as careful about passing on deformed fish as they used to be. Most all of the common danios have been farmed for decades so genetic faults are going to show up in spawns.
Personally, I would not accept the fish and would return it for one that is fully formed. I wouldn't allow a fish like this to breed to pass the defect on so no reason it should be in your school. The only way stores are going to stop housing and selling deformed fish is by the customers not accepting them. Once the stores complain and stop buying the deformed fish, the wholesalers will get back to their suppliers who should get back to their suppliers ( or farms) and hopefully, when enough people do this, we get better quality fish back into the hobby.