Well, he said "extrusion speed" so I assumed that's want he meant
Also the values "40 or 60 mm/s" given translate into 2400 to 3600mm/min which would be rather high feedrates (travel speeds).
As far as I can tell, Z-Suite usually uses something like 1200 mm/min as feedrate for the contour and 2400 mm/min for the infill.
Besides, using material dependent extrusion multipliers is a common feature of slicers. E.g. the Simplify3D troubleshooting guide says:
It is typical for PLA to print with an extrusion multiplier near 0.9, while ABS tends to have extrusion multipliers closer to 1.0.
There is actually a G-Code command to set the extrusion multiplier (E.g. "M221 S70" sets the extrusion multiplier to 70%). IdeaMaker uses it for different material profiles.
This being said, a fixed feedrate (travel speed) wouldn't make much sense as it changes quite a bit depending on the movement/action performed. E.g. movements without extrusion should be fast, movements while printing the contour should be slower than movements printing the infill. So the only way feasible to change the feedrate would be a multiplier but I just don't think it would make much sense. If at all, it could be used to slow the printing process down but I'm not sure if this is really desirable.
[EDIT]
About the relation between feedrate and extrusion: the feedrate is a speed (position change per time) value that defines the travel speed of the following movement commands. The extrusion value however is a position value that is used in movement/extrusion commands like the X/Y coordinate. In plain G-Code this looks like this:
G1 F1200 X71.838 Y101.911 E1.928
G1 F1200 X71.847 Y101.834 E1.931
G1 F1200 X71.877 Y101.753 E1.934"F" is the feedrate, so "F1200" means that the X/Y/Z position should be moved to with 1200mm/minute. X/Y/Z/E are the according position values in mm.
You can see how this extrusion value increases continuously during extrusion. It only decreases for retraction moves. As all the other coordinates, it can be set (redefined, not moved) to a new value though.
E.g. some slicers (including Z-Suite) set the extrude value to 0 at each layer change.
Anyway, even the though some details are different in ZCode, you can see in the GCode example that it would be very easy to change the feedrate values with a multiplier but this wouldn't have an influence on the material extruded, just on the movement/printing speed. Actually manipulating the extrusion values is a bit trickier because of the resetting of the value and the retract/unretract moves but this is what RaftAway does for the 1st model layer (and therefore also could do for the rest of the model).
