I'm not saying it's not different. I am just saying that if someone is concerned about efficiency of the CCM T2 vs the CCM S6 it may not matter as much *what* the spring is if most people aren't going to have access to different springs or aren't going to do more than air it up and shoot.
To me it seems like it depends on what question you are answering. You could ask 1) What's the efficiency of the markers out of the box and how do they compare? or you could ask 2) How do we make them most efficient? or even 3) Try to postulate what differences in the construction of the markers is the cause behind the efficiency.
If you are going for a deeper analysis (2 or 3) then I see where measuring the spring becomes essential. For question 1...maybe not so much.