Nearly. It almost certainly never even touched IT.
The issue is that marketing is organizationally separate from IT and doesn't want to interact with them. IT is probably behind a slow, outsourced ticket based process and will take weeks to do a simple thing. They may also have random opinions about stuff marketing doesn't want them to have opinions about. So building out promos like this is delegated to SaaS services or contractors who also have no relationship with corporate IT. Then nobody in marketing really knows or cares what a subdomain is, because everything they do is just searching Google or clicking links. They never look at the address bar because it's always full of meaningless junk so why would they or anyone else care what's in it?
Anti-phishing training doesn't make sense, when you look at how people really use the internet. Not many people look at the actual text of a URL. The best anti-phishing training is "go to google and type what you're looking for, only click links from there" and not "carefully examine the domain name to try and intuit if it's owned by the organization you think it is".