No, HL does not consider return currents. A power plane and a GND plane are equivalent as far as HyperLynx is concerned. For the most part that's a reasonable approximation, as long as the GND and power plane are well decoupled (lots of caps).
Beware though that in the real world, a power plane will be noisier. That's why Micron recommends referencing DQ/DQS to GND. Address/cmd can be referenced to Vdd if necessary - because A/C is less sensitive to noise (larger bit period).