No security is full proof, but they call it "hardening the target" when you reduce your attack surface.
The way you actually reduce attack surface is to take the critical pieces off of it and minimize the paths to be watched, not the whole system. That would be like ensuring it is possible to close off all of the highways into Washington DC to response time for the three federal branches. If it was actually that damn important they would make and use secure tunnels. The only added benefit is an excuse to shut out protesters.
Not to mention mere independence isn't everything for system functionalities. Going to muscle powered factories to remove logistical dependence on power would be an obviously stupid move for example because the performance is so much worse. It is "selling ceramic knives that cannot be sharpened as never needing it" marketing deception of trying to cast a flaw as a strength.
Russia doesn't need pretense for control.
This is actually most useful for security. At least if you are attacked your national network will survive.