I do not think that you would need to submit the old passports in the application unless requested.
The purpose of the requirements are listed in this cic guideline:
Passport:
Purpose
To confirm identity
Document requirements
A clear and legible copy of the bio data page must be provided.
Individuals who must submit this documentation
The principal applicant
Their spouse or common-law partner
Their accompanying dependent children
In some instance, they might ask for a supplemental scanned copy of your visa stamps on old passports but they will not be a requirement at the onset. The purpose they are asking for your passport is for them to have a legally accepted document that they can use to verify your identity.
When I submitted my application, they are just requesting for the valid passport with the bio data page, visa stamps and visa of that particular passport. They did not mention you must attach all your old passports because there will be instances that old passports have been lost etc.
Hope this helps