That's impressive. I didn't know any of the free supplementary cards offered the perks. I used to have an IDC Centurion which included the extra Cent for my husband and even an extra black card for business expenses, plus a bunch of extra Platinum and Gold cards for no additional fee. However, there were no airline elite perks nor extra hotel perks at that time (this is some years ago before the IDC Cent fee increased). It did give the extra Priority Pass, which IDC Platinum still does.

I would love to keep my husband's US Cent at the previous lower fee but the only thing it really gives us is DL Platinum for both of us and we don't get enough value from that with our current travel pattern for $2500. Maybe in future we would. Otherwise, we can manage fine with the hotel and Avis status just on my account.