Heat is a result of current through the H-bridge.
Typical volt drop (losses) of the ancient L298 is 2.55volt at 1 Amp and 3.7volt at 2Amp.
If you are driving a 500mA motor, then generated heat in the chip might only be 1watt.
But the chip could blow it's top if you power the chip from 12volt, and connect a 3 ohm low-impedance stepper to it. Then it has to dissipate more than 11 watt. And you have to be sure that that 2.7Amp is not going to damage your stepper.
A current controlled stepper driver doesn't have those problems.
Average stepper coil current is kept the same, independent of supply voltage and stepper speed.
Leo..