> when they can just share a pdf.
I assume your question was in good faith, but the information needed to support an entire platform like this is not as simple as sharing a PDF. I’ve spent parts of my career working on much simpler platforms than an entire Apple laptop where we would have to work through 10,000 page PDFs documenting registers and even that was not enough to get the full picture of the system. You have to work through provided code samples and then eventually get the vendor’s engineers to look into problems that couldn’t be resolved through the documentation, where they would go look into the other teams and their sources to discover the answer.
The market for people who want to install Linux on a Mac laptop is very tiny. The honest answer is that it’s not worth the huge effort investment needed to document an entire platform for public consumption.
I don’t think many people realize how easily Apple could have locked down the laptop to be able to not run any alternate OS at all and the number of lost sales would be so negligibly small as to not matter. They chose to leave it open.