Just like for the storefront, you can still copy-paste the backend views into your application if you want to override them. However, this approach is quite hard to maintain, since it would prevent you to get any Solidus upgrades to the backend for views that have been overridden. It becomes even more complex when you consider all the different overrides applied to the backend by Solidus extensions. Deface is a declarative, maintainable way of patching backend views while still benefitting from Solidus upgrades.