Not entirely correct. There are some lines of tigers that ARE genetic, like Michael Jolliff's tigers. I have them and they are re-produceable. I purchased my founding male from Michael.
Also, some black backs ARE genetic. I've just produced a clutch of black backs from black back parents. Black back cinnie with all black back cinnie babies to black back normal with all black back normal babies.
Here's a male "normal" from that clutch.
While the black back may not be a recognized "morph", when it's genetic, it can be used to enhance other projects.