I would have done the same as you. I would have called the teacher on my own and passed along the information. It would be more convenient and more efficient for me that way. Which is better for the kids. I like to know and take care of these types of things asap. And having to coordinate times with the other person just makes things complicated. Thankfully my ex is fine with this. And I keep him in the loop. He is more then welcome to call the teachers on his own.
Maybe in the future you can get around this by making the call by yourself and then offer to schedule an additional meeting with all of you for the future if the problem with your child does not get resolved.
To me it seems like your ex cares more about how it appears for the teacher then the actual issue with your child. If i was her, I would have been focused on what the teacher said about my child as opposed to you making it look like shes an absent parent.
I am dealing with another mom (yup shes a walkaway) that has a similar attitude. She is bat sh!t crazy. And the things your ex says "We need to do everything together. anything less is unacceptable" are things controlling but incompetent people say. Your wife sounds controlling and incompetent and concerned only about appearances.