Well, give me a break!
I believe nobody knows better than CIC about how the points are assigned! right?
While I was filling in my application, I had been calling CIC almost everyday to get information about how to fill in the forms .. (BTW, they are very responsive to these kind of questions).
The CIC agent told me that the points will be assigned based on the experience claimed for the NOC which the applicant has chosen as the primary NOC. However, it is up to the visa officer to grant the points if he/she is convinced that the other NOC(s) the applicant has claimed experience for are related to the primary NOC.
In case the NOCs are not related .. no points should be granted for the NOC other than the primary, which is very rare to find people moving from job to another unrelated job.
I mean .. you might be working as a Business Analyst for 4 years, then you got promoted and worked for 2 years as a Project Manager .. The NOCs are different, however, the job descriptions/duties are overlapping .. thus, the officer might grant you the point for the full 6 years!
I hope this helps!.