This is not an Apple thing... For ages CPUs and I think GPUs, too, are basically the same thing between many different models.
Then more expensive versions just get more cores unlocked, higher frequency allowed, etc.
That's called binning, the unit goes through some testing and components that don't pass get shunted away (hardware or firmware) because they're known to behave incorrectly. Better that than throwing it into a trash.
Blow the fuse/hack the firmware and you can unlock these because the hardware is there, but it's likely that it doesn't operate entirely correctly (especially under duress), even though it may appear to work at first blush.
https://lwn.net/Articles/884876/ https://news.ycombinator.com/item?id=30394918
A solid mechanism to enable/disable these features on demand would make the situation a lot better. You could pay just for the upgrade instead of the whole chip, either permanently or only when you need it and pay per use.
But the reality is that in practice this mechanism will probably not work to the advantage of the end user. It will focus entirely on the company's bottom line and open up new avenues for abuse. If your hardware is linked to a license and to the manufacturer forever, you'll never own it. Unless the legal framework enforces the rights of the consumer under threat of drastic fines for the manufacturer, we're just forgoing real ownership.
But the thing now with "pay to unlock more cores" is... interesting.
They'd probably love to turn that into a subscription, too.
I think Intel abused this at least once, back in the days when they had ridiculously good yields across the board, but let's not generalize in absence of evidence.