Call stacks help form a mental model for some people. It’s a way to help get an initial grip on the topic, one of many. Teaching usually involves many simplified models which in my experience helps a lot with initial understanding.
We don't need detailed call stacks to help with understanding recursion. Just the somewhat more abstract concept of a procedure/function activation. Calling a function suspends the caller and create a new activation for the callee. When the callee returns, it's activation is disposed and suspended color resumes in its original activation.
The point was pedagogical, sometimes the “best” explanation just doesn’t work for a student. Some might get confused about where the state of the caller goes and get hung up.
