This offer seems to be back. Free $141 and should be easy to meet the spend requirement.
From the website:
*Cash back promotion: The cash back offer is available when you apply and are approved for a new Low Rate credit card from 16th April 2019 and 31st July 2019 and spend $400 on eligible purchases within 90 days from card approval. Eligible purchases do not include fees, cash, cash equivalent transactions, BPAY, refunds and balance transfers debited from the card account. Only one cash back will be paid per customer. The $200 cashback will be paid as a statement credit to your respective Low Rate credit card account within 60 days of meeting minimum spend criteria. Existing Westpac customers who currently hold a Low Rate credit card, or who have held one in the last 12 months and packaged cards are not eligible for this offer. Cannot be used in conjunction with the balance transfer promotion.
Good deal, you will eventually get the cashback, but horrible bank to deal with.