Comment by Hackbraten

> Why?

Because 1. it helps with debugging at development time; 2. it may take unreasonable effort to disable, possibly from a hardware team's point of view with no direct security background; 3. it may be worth keeping around for future patching flexibility.

Source: [0]

> Apple isnt exactly a small family business and this is quite the drastic "feature" to be left enabled by accident.

No matter how large and hierarchical a company is, there will always be teams making hundreds of small, apparently localized decisions in their own line of work, without consulting anyone outside their team, and without seriously considering ramifications. It's humans all the way down.

> How would one look from your perspective?

A feature where you poke a seemingly random 64-bit value into an apparently arbitrary memory address, which grants you access to something you wouldn't normally have. That'd be a backdoor to me.

In the case at hand, the feature neither has a hidden MMIO address (it's discoverable in a small-ish search space), nor does it require a secret knock (but instead apparently just a somewhat convoluted checksum.)

[0]: https://social.treehouse.systems/@marcan/111656703871982875