It's not totally clear and we're in uncharted territory as Apple has never tried to collect commissions on payments that were not made with IAP. However, it is

It's not totally clear and we're in uncharted territory as Apple has never tried to collect commissions on payments that were not made with IAP. However, it is worth noting that the actual text of the developer agreement (quoted on page 32 of the ruling) says the following: "For sales of Licensed Applications to End-Users located in those countries listed in Exhibit B, Section 1 of this Schedule 2 as updated from time to time via the App Store Connect site, Apple shall be entitled to a commission equal to thirty percent (30%) of all prices payable by each End-User." Note that it just says "all prices payable by each End-User", there is no distinction in the contract between purchases made internally in the app and payments made externally via a website. To the extent that the court has found that this contract is indeed enforceable (minus the anti-steering provision), that would suggest to me that taking you outside of the app to pay via a website might not make a difference to the commission owed. But I suspect this is the kind of thing that very expensive lawyers are going to have to litigate before we get a definitive answer.