If you had 2 freewheels:
for example 72p front and same in back.
So 360/72=5 degrees between each engagement point. Lets take stock gearing 18/15=1.2 so 5/1.2=4.16 rear engagement "makes" 4.16 degrees between every engagement point. So if your pedal moves 5 degrees, front freewheel engages, then you move more 4.16 degrees, the rear freewheel engages. Between 2 engagement point will be 5+4.16=9.166 degrees.
72p freewheel on rear:
360/72=5 18/15=1.2 5/1.2=4.16 degrees moves crank before engagement.
72p freewheel on front:
360/72=5 degrees moves crank before engagement.
So with both freewheels you don't have really more engagement points.