Hi thecoolguysam,
My wife could not assume last name in her SIN even though it was updated in her DL and OHIP. The SIN office mentioned that she needs to get it updated in her PR Card first and then they change it. However, the funny thing is that based on her DL update, the SIN office added both first name and last name in her last name.
SIN and PR Card system should be applicable Nationwide which means it should be following same rule. However, as per you statement, you could change the SIN first and then PR Card.
Any hints on my problem and how to proceed further?