I'm assuming you can use the store credit for purchasing things like their phone covers etc.
T&C's:
Get $100 Google Store credit when you purchase Pixel 4a with 5G from Google Store Australia. Customers will receive an email notifying them Google Store credit is added to their account approximately 3 weeks from the order shipment date. Offer valid starting on 05/11/2020 12am AEDT through 30/11/2020 at 11:59pm AEDT. Available only to Australia residents with shipping addresses in Australia. Must be age 18 or older to be eligible. Recipients must have Google Pay profiles registered to the country where purchase was made in order for the Google Store credit to be issued and once issued will be in the currency of the country where purchase was made. The Google Store credit can only be used in the country of purchase. Limit 2 per customer. Offer isn’t valid if the device (or any part of the order) is returned. It’s non-transferable, and not valid for cash or a cash equivalent. Available only while supplies last. Shipping charges may apply at checkout. Void where prohibited. Google Store credit expires on 30 November 2021 at 11:59pm AEDT.
No, future Pixel phones aren’t exempt from Google Photos’ money grab
https://www.theverge.com/2020/11/12/21562908/google-future-p…