Google Play Pre-Register Rewards Support?

Google Play claims that the implementation of their new “pre-registration rewards” has around the same implementation as their “promo codes”. Noting that promo codes are supported by Unity IAPs. I wished to ask if I could also expect the “pre-registration rewards” to work through Unity IAPs, and if so, where I could read more about it?

Source pre-registration rewards: Build awareness for your apps with pre-registration - Play Console Help

Source Unity-IAP release notes which state support for “promo codes”:

Bump, There are no clue for this.