Dell, HP/Compaq, Gateway, Lenovo/IBM, Asus, and most other companies publish service manuals for their products, including their enterprise servers as a free download. Unless you pay money to Apple to get your business established as an authroized repair center for their products, you ain't getting a service manual.
Buying parts from the manufacturers to do the repairs is legit easy as fuck and hassle free.
The only company that I can think of that does shady ass shit is HP for their printers. The lengths they go through to force you to buy only HP ink carts is ridiculous 'cause their shit is horribly overpriced. Oh, and Dell started using power supplies with non-standard connectors on some of their desktops, something they did almost 20 years ago but stopped doing for years. But even with that, there's ways around it and Dell won't penalize you if you try to get warranty service for a machine that you swapped a PSU on.
Aside from that? Nah. Apple is pretty much alone in this shit.