Collected the card yesterday.
After read thru the cash back T&C from the booklet given, T&C no.4 stated supplementary card also entitled for cash back. Based on my understanding, the cash back is only for Principal card. Is it true?

4. Subject to the eligibility criteria specified above, transactions made by
the Supplementary Cardmember will also be entitled to the Cash Back,
where the Supplementary Card’s spending will be accumulated with
the Principal Card’s spending and the Cash Back will only be credited to
the Principal Card’s account.

Thanks! Then I may apply sup card for my wife.