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? And how do I test it?

Source pre-registration rewards:

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

You would test through Google resources in Alpha/Beta release, we don’t have specific code in place. It should work the same as Promotions, but haven’t tested.