Stingrays are sensitive animals and they could not endure that type of mutilation. Stingrays also have an amazing ability to regenerate their disc, which would further recognize 'batman rays' to be a developmental disfunction.
Batman Rays are the result of a defect during embryonic development of the disc. The frontal area of the disc fails to fuse together. This morph is very uncommon, and no one to date has been able to reproduce these rays with success. Much like Albino or Xanthic morphs, these rays are a genetic misfit, and are usually only birthed in captivity because the survival rate of a deficient animal in the wild is next to none. This is due to predation and competition for food. They live just normal stingray and needing the same fish supplies.
These rays move, eat, and act like normal stingrays. Special care must be provided as they tend to have a harder time competing for food. Beyond the few that are being kept in captivity, very little is known about the Batman Ray. We can assume that it is a genetic mutation, similar to a 'cleft lip' in a human, and that it is in no way man-made. These stingrays demand a very high price due to rarity.
There is no known genetic component to cleft lips in humans, and batman morphology in stingrays almost certainly has nothing to do with genetics.