That's a misleading number. In most other cases where we are using electricity--motors, CPUs, lighting, etc--we consider the heat generated to be inefficiency. It might be more accurate to say that electric resistance heating is 100% inefficient.

If you're using resistance heating to heat your home, using electricity that's originally produced by natural gas, then you're using more natural gas compared to burning that gas for heat directly in a home furnace. Now, electric resistance heating can be a choice when it's fed by clean electrical sources otherwise. Even then, though, you would prefer a heat pump if possible.