If AWS is deprecating something, then it's likely that literally no one was using it and the few that might have been were given complimentary consulting to move them off of it.
I mean, you're probably right - that none of their $100m contracts were using the feature. But otherwise, why remove it? What was it costing them in maintenance and support? Were there actually any security issues?
There's no way this had any real users if it is being quietly turned off.