SMD Resistor Power Rating Calculation
These are current-sense resistors, they won't ever have the full 3.3V across them, for the reasons you've identified.  If you study the datasheet you should find the nominal voltages for ISENA and ISENB, and substitute these in to your calculations.  Spoiler alert: you'll very likely need larger than 0603 and you'd be well advised to specify resistors that are designed for current-sense purposes, as these are likely to be more stable than general purpose parts.