The linked program ("Mini Apps Partner") is for you, not for the developer of the mini app.

I make a game for your arcade, and players pay cash to add credits to my game.

The status quo: Player pays £1, Apple takes their 30% cut, you get 70p, take another 30% cut, and give me 49p

What this programme entails: player pays £1, Apple takes a 15% cut, you get 85p, and hopefully pass on some of that extra money to me too.

The gotchas are:

1. it has to be your app and my mini game. This is about lightening the load of all the intermediaries, not about you cheesing an extra 15%

2. It has to be the player buying credits for my game specifically. If you sell “ArcadeBux” redeemable for credits on any game at your arcade, you’re not an intermediary, you’re the vendor.

15% is the normal rate for the App Store. Only developers earning above $1MM/yr through the App Store have to pay 30%, the vast majority of developers only pay 15%.