I think there is still the question, though, of why the same method that saves the field keys when you manually save a post in the WordPress admin could not be replicated for when you create a post programmatically.
I understand why the field keys are faster, but sometimes you don’t want to hard code those values. It makes it harder to read the code (imagine handing your code over to a new developer, who has to determine what all those field keys are referring to), and it’s not as portable.
Since this is such a common issue for ACF users, it raises the question – why is there no way to associate field keys with a programmatically generated post? There is nothing special about manually saving a post that means it should be the only way for ACF to generate these meta values.