Baby wholphin

This is apparently what you get when you cross a whale and a dolphin. I’m a bit confused, though. If something can produce offspring that can produce offspring, isn’t that the standard definition of a species (a category of biological classification ranking immediately below the genus or subgenus, comprising related organisms or populations potentially capable of interbreeding, and being designated by a binomial that consists of the name of a genus followed by a Latin or latinized uncapitalized noun or adjective agreeing grammatically with the genus name)? For example, donkeys and horses are not the same species because their offspring are sterile.
The same thing goes for ligers and tigons. It is hard to think of lions and tigers as being the same species, but doesn’t their ability to produce offspring capable of reproduction make them just that?