bigdog wrote: ... ASTM C1063-08 but it appears to only specify spacing for "On center along the framing member" and I see nothing for solid sheathing.
David,
That's because the metal lath should be attached to the framing, only, and the more staples, the less space behind the metal lath for the stucco to be scratched into and key behind.
Nailing/stapling every 7 inches throughout the sheathing area would be way too many staples and very little furred out area to get stucco behind the metal lath - another requirement you will find in that standard is that the metal lath be fully embedded in the stucco ... otherwise the metal lath will rust out.
The nail spacing is under revision, but the above regarding too many nails will still hold true.