Who would've thought? This isn’t going to fly with the EU.
Article 5.3 of the Digital Markets Act (DMA): "The gatekeeper shall not prevent business users from offering the same products or services to end users through third-party online intermediation services or through their own direct online sales channel at prices or conditions that are different from those offered through the online intermediation services of the gatekeeper."
Friendly reminder that you can sideload apps without jailbreaking or paying for a dev account using TrollStore, which utilises core trust bugs to bypass/spoof some app validation keys, on a iPhone XR or newer on iOS 14.0 up to 16.6.1. (ANY version for iPhone X and older)
Install guide: Trollstore
Your description matches my understanding of the process (as someone who left iOS development a few years ago).
I don’t think that the DMA is technical enough to differentiate in this precise manner. Keep in mind that it was written by lawmakers and politicians who mostly don’t know how to even use a smartphone. They'd think that a certificate is a piece of paper with fancy signatures on it.