The sacrificial anodes in water heaters are designed to reduce corrosion in the water jacket and really have no bearing on the pipe connections outside of the tank.

The dielectric fittings are a good idea for the tank connections in the case of dissimilar metals and will make the outside connections less likely to corrode and leak, but the internal anode is for the small bits and pieces that make it into the tank and may affect the tank itself. The sacrificial anode is softer and easier to attack and protects the tank by letting itself be eaten by the chemical or electrical processes that may occur in the tank water.

Bountyhunter