In assymetric flight you are sideslipping, so heading and track do differ.
The challenge for asymmetric flight is to use the appropriate combination of rudder and bank so that you do
not slip.
If you fly wings level you will slip into to dead engine. If you use too much bank into the live engine, you will slip into the live engine. If you get the combination right, you will not slip.
(The position of the balance ball will not be in the middle in a no-slip condition with asymmetric power.)