This is the link that lists the required original documents for SIN application (it lists both the requirements for mail and in-person).
https://www.canada.ca/en/employment-social-development/services/sin/before-applying.html#primary
A quick Command-F (Ctrl-F) shows the word "address" is nowhere to be found on the site. When you download the application for mailing the form in, it lists the same information and includes a checklist. Again, nothing about an address.
Yes ur right for mail applicants they don’t require address proof. But for ppl who apply via online they need address proof. But ur case they mentioned SIN online request. Which makes confusion. Due to this pandemic situation we can’t do anything other than jus wait. !!