IRCC does not mention uploading old passports. However, in the past some applicants have received ADRs to submit old passport or valid visas in the old passports and scans of the entire current passport, even if it is blank. Also read the instructions next to the upload window.
Also to avoid any ADRs, you should upload your current passport, and any markings and valid visas in your old passport. When you get an ADR, it adds tp your processing time.
The requirements for all documents required is available athttps://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/permanent-residence/express-entry/applications-received-on-after-january-1-2016-completeness-check.html
However, some of it differs from the instructions next to the upload window in your MyCIC account. So follow the applications prompts which requires all markings and visas. Since you can have valid visas even on expired passports, you should submit scans of old passports, if it has markings
The instructions on your MyCIC state:
Where as the instructions as per the link shared above state:
If you read both the instructions, you should err in providing more than what is asked and the reasonable interpretation would be to provide a scan of the "biographical pages, and pages with visas, markings and stamps of your current and expired passports, and all pages of the current passport."
Passport is just an identity documents, and does not have any impact on your eligibility. However, when there is an ambiguity, always provide more and disclose more than what is essential, if it doesn't harm you.