I don't think the emphasis here is just on "single occupation", but it is on "relevant to the single occupation".
And this is the contentious issue, I checked all SINP webpages and forum threads here and there is so far no conclusive answer of whether all jobs for which points are claimed must be of the single identical noc as the one selected as part of the application. I asked SINP and wait to hear back, but when taking the wording literally then the following should be acceptable as well:
Someone files an EOI with NOC 0601, corporate sales manager. One claims points for all 9 years of previous work experience within the past 10 years. One job matches with NOC6221, technical sales specialist, and other jobs match with NOC 0601, corporate sales manager. Because 6221 is RELEVANT to 0601, and is basically showing a natural progression from a junior sales role to a senior sales manager role, the requirements set forth by SINP should be met, which is that the jobs for which points are claimed, should be relevant to the chosen application NOC. Hence one should be able to claim points for both NOC 6221 and NOC 0601 with NOC 0601 chosen as the main NOC.
The above would obviously not apply if NOC 0601, senior sales manager, was chosen as part of the application and if then the applicant claimed points for, for example, computer programmer or registered nurse because those jobs are not RELEVANT.
This is my reading and understanding of the deliberate working of SINP. But I asked them by email for clarification, I hope to hear back from them and will be happy to share the findings.