You should declare any family member in application package (whether accompanying or not) in order to allow them to gain PR status either at same time with principal applicant or later. If you don't include them into immigration package, you would not be able to initiate their migration process later.
Also, I have a trouble understanding "non-accompanying spouse" definition.
Does it mean your spouse is not intended to land at the same time as you? In theory it is possible to land, apply for PR card and go back to own country by one spouse (and even both, and look for job opportunities from your own country).
Is it mean then you live in common-law partnership but think about to marry later? OK, why not to declare it as common law union, marry and then inform the CIC?
Is it mean that you plan to change your marital status soon? OK, you can either wait until process is done and apply, or initiate the process and inform the CIC.