Question is how fragile the upgrade process is in large installations. In other enterprise software messing around with large amounts of data I've seen the smallest things break the install and leaving the OPs team rolling back. Was like SharePoint in the past, you were rolling a dice when upgrading it.
It's incredibly fragile. It breaks a vast majority of the time and takes multiple rounds of support on-call to upgrade typically.
Unsurprising for a fourth tier on-prem created by cutting a continuously deployed application into releases.
The GitHub blog had an article saying that all patches must pass for github.com before merge but the GitHub Enterprise tests have a three day window to be rectified.