Yes, because the pad risers are typically airfoil/oval shaped, while the stem spacers are cylinders. Depending on your bike and the setup, a slammed stem may also benefit from the toptube or bento filling in behind the stem. A middle ground is an upward slanted stem, which will appear as an elongated oval to the wind.
Aero aside, put the base bar and the aero bar where they need to be for optimal utility. IMO, the base bar position should replicate the hoods position. It's going to be used for cornering, climbing, and out-of-the-saddle efforts. It doesn't need to be aero....that's what the aero bar position is for.
ECMGN Therapy Silicon Valley: Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)