It's a fairly comprehensive article, but it does seem to veer too far into "This happens and then this happens and then this happens" without providing a great deal of insight. There's oddness like "the Memory Management Unit (MMU), if it exists", when we can pretty much take as given that it does for the platforms he's discussing. And then "Some speculate that this feature is maintained in order to ensure that the platform can boot legacy code such as MS-DOS" - isn't the author in a position to give us facts rather than speculation?
I did learn things from this, but it's not especially well written. I think there's still plenty of scope for a series of articles that explains this with more background.