How is it constant voltage if it isn't regulated?
It isn’t, it is a data sheet written by someone who’s grasp of English is as poor as their grasp of electronics.
It makes absolutely no sense regulating the voltage into a constant current drive, you might as well feed an unregulated voltage into it and then it has a wider range of constant current capabilities.
If indeed they regulate the voltage before putting it into the constant current supply then they are idiots.