If a job doesn't require the level of security clearance that only Canadian citizens can pass, then those jobs shouldn't require Canadian citizenship to begin with. Can you think of a counter-example?
Not sure if this is a valid example but check this out :CSIS is a very specific example. Most positions do not require the same clearance level as an employee of CSIS.
https://emploisfp-psjobs.cfp-psc.gc.ca/psrs-srfp/applicant/page1800?poster=1630886
This job is with the RCMP and it requires a Top Secret Security Clearance (that is usually only given to Canadian Citizens) but all "Persons residing in Canada and Canadian citizens residing abroad" can apply for this job.