Ingress Admission Controller - simple question

I think my biggest question is where to find the documentation that would describe why I get many UPDATE operations sent to my webhook after the initial CREATE of an Ingress.

I am mostly doing validation, but I think I need to validate UPDATE operations when developers apply changes to their Ingresses. But when I turned on UPDATE operations I got a lot of unexpected transactions.

Cluster information:

Kubernetes version: 1.15.5
Cloud being used: bare-metal
Installation method: Rancher
Host OS: linux
CNI and version: canal
CRI and version: docker