Genetically, that's not quite right. It is possible for both parents to show white skin but carry yellow skin. That's the trouble with recessive genes-- you can remove every bird that shows the trait, but finding the carriers takes a lot more effort.
But in the case of McMurray's flock, if they...
"Certified Ameraucanas"-- is it on the McMurray website somewhere? Or in the paper catalog? I wanted to read what they had to say about it, but I'm having trouble finding it.
I can find articles from 2021 about McMurray getting 5 breeds certified by the American Poultry Association, but I can't...
Have you read the actual SOP description? In the physical book?
If you have, please tell me what it does say about leg color.
I have not (don't care enough to pay the usual high price.)
But if I am trying to track it down from other sources, I find things like this:
McMurray sells "Blue...
And the splash color will too, when it is officially recognized:
https://amerpoultryassn.com/2021/10/large-fowl-splash-ameraucana-approval-process/
"The shanks should be bluish slate."
I would agree that Splash Ameraucanas can indeed be Ameracaunas. Having the splash color does not automatically make the bird an Easter Egger. But of course having splash coloration does not automatically make the bird an Ameraucana either (Splash Cochins exist too, and Splash Andalusians, and...