linking is not mandatory. if you haven't linked yet, requests will be sent by email or mail as indicated in your IMM0008, ie, they will continue to send you email for requests.In my case AOR was received 10 days back and Sponsor email 3 days back. Still not able to link to IRCC account. Is there any other method for receiving medicals? they won't send an email to the applicant?
if down the road, you can link the application, you will ONLY receive requests in myIRCC account. and if the request is for documents, a place holder will open up for you to upload.
'HOW TO LINK AN APPLICATION TO CIC ACCOUNT - STEP BY STEP INSTRUCTION'