Yeah smart people work at Epic, and smart people with ties to the midwest end up staying longer than 5-6 years. Epic does get a lot of things right, especially the code review process. If someone saw a reference to ^ER in code being committed, you can bet that it would get changed. The linter (HXPARSE) would actually prevent you from moving code with certain global references.
(You're telling me though you never came across "end-user" API-level code that was directly digging around in ^ER, ^ER1? Hahah)