The fact that WN actually bothered to call, which takes time and costs money, suggests that the issue is taken a bit more seriously than ordinary or that it received multiple reports of the same incident. Cut & paste emails cost close to nothing to generate.

But, I still suspect that WN is fine with the ambiguity of not assigning seats but allowing various informal seat assigning to take place. It is poor service, but not likely to change as WN thinks it has a happy medium.