It's weird - I don't think I remember ever seeing corp.com as an example from Microsoft - they usually used contoso.com or microsoft.com. I do remember reading books that used corp.com however, but they weren't printed by Microsoft.
This may be an issue where only networks that have been around for a very long time have this issue due to preserving configurations through many years/cycles of upgrades. Unfortunately, there are many, many such networks.
