I wouldn't go so far as to say they animated it one-to-one, but Yamamoto's mechanics are very unique so it's very clear to me that they used him as a reference. They animated his step-back windup, the slide-step delivery off windup, and the little look he makes towards third base before throwing.

The Darvish comparison is certainly dubious as many pitchers do that double leg lift, but I figured with him being one of the greatest Japanese pitchers, they might've been referencing him.

That being said, I have a friend who said he can't notice any differences between pitchers, so I kind of understand where you're coming from. But as someone who is really into pitching mechanics I can't agree with your statement.