First, it's about data transfer speeds. I don't think... anyone else in my extended family, and certainly none of the iPhone users, use a cable to transfer data frequently.
But more importantly - the subtitle of the article says that only the pro models offer faster charging speeds. Despite the article being exclusively about data transfer speeds.
I use USB-C for data heavy applications all the time. I'm running a monitor on one right now.
This means that a bunch of people are just going to end up with cables that are once again locked into their iPhone ecosystem and can't be used for any other purpose. I find it hard to believe that this is anything but Apple thumbing their nose at the new EU regulations by intentionally making their "compliant" cables useless.
I highly doubt the limitation is going to be at the cable. They are generally known for their high quality production capabilities, meaning they would have to actively make the cable worse (and likely cost more while doing so.)
They are likely going to simply limit the controller to 2.0 speeds.