When you buy an Apple product it has a number on it Axxxx and a serial number somewhere. That's all you need to identify your product to anyone. That includes service manuals and spare parts.
And as far as warranty registration goes, they register it at the point of sale/activation as the warranty starting. Job done. No humans / lookups / anything required. It just happens.
As for finding service manuals and user manuals - maybe what they need isn't the web but FTP. I mean, if it were still supported by browsers. I remember when some vendors just used to have folders with PDFs you could browse.
The problem with "the web" is that this is no longer a website, but a content management system, or worse, a "customer engagement platform" that is hostile to creating a folder full of PDFs that have stable links. They probably still have that FTP site in a webified form somewhere for service partners, just not for Joe Public.