You mean where the ASRGs state:
- Apps may use in-app purchase currencies to enable customers to “tip” digital content providers in the app.
Note 'digital content provider', a 3rd party, not 'the app's developer'.
As an unpaid umpire, my opinion is that tipping you for your app doesn't seem to be in line with that statement. An example where it would apply is if you make a chat app, and one of your users makes a comment that other users want to support by tipping that user.
I agree with KMT that the guideline he quoted is intended for third parties. That said, I don’t think there is any reason why an IAP could not also ‘tip’ the app developer. To be consistent with the intent of other guidelines it might be best to issue ‘I tipped the developer’ points (that do nothing) and sell them simply as a consumable IAP available in any quantity for $0.99 each. Also - you need to use the price information downloaded in a purchaseRequest since only in the US is that the correct price for your buttons.