Also sometimes flipping feature flags can be faster than doing a rollback, especially if multiple systems are involved.

I would argue that if flipping a feature flag isn't faster than doing a rollback, your feature flags are not functional. They should be essentially instantaneous and the first thing to reach for as soon as you've identified a problem.

Also sometimes flipping feature flags can be faster than doing a rollback, especially if multiple systems are involved.

This I totally agree with. Using feature flags well requires some discipline on the team's part to stay on top of them and remove them once they've served their purpose.