compress the shock fully. Now release it. Does the shaft pop back out again on its own?? If so, then they need to be bled, refer to manufactureers guide.
I do not think you are right in this point...
Basicly we are using single-tube shock dampers with compensation room for piston volume.
The air bladder over the diaphragm is for volume compensation of the piston!
If the shock is fully extended the piston does not need any room in the shock. now if you compress the shock, the space of the piston has to be compensated. since you will not be able to compress the shock fluid itselfe, the air bladder over the diaphragm is compressed. the air now beeing compessed will push the piston back out! how far depends on length and diameter of piston, the shock fluids viscosity and piston hole size, the smoothness of the shock and size of the bladder.
Now if you push the piston all the way in before you tighten the shock cap (resulting in a air tight shock) your diaphragm is uncompressed and the bladder is not under pressure. now if you pull out the piston your diaphragm will be pulled in the shockbody. but the diaphragm is not designed to be pulled! it is designed to be compressed!
Only push the piston in 15mm to half the length before tighten the shock cap, to keep the diaphragm and air bladder working the way they should!
Just a little advice:
do not care about it to much...
since the shocks are not
really air tight, after 10 minutes of bumping and jumping around the track, oil heating up and cooling down, there will be no difference in how you build the shock...