"T series Thinkpads used to be some of the most repairable laptops around. Not only were parts available, but the repair and maintenance manuals were in the Internet, and for free."
That's still the case, on the whole. I only see enterprise class kit, and most of it is pretty easily repairable, full parts/repair manuals available to all, plenty of Lenvo created videos on YouTube demonstrating the parts replacement process. Where things have changed from the IBM days is primarily in the consumer grade kit and to an extent in the enterprise kir where, for example, on some of the cheaper models the RAM is on the system board, possibly with no expansion SODIMM socket, but most will at least have one SODIMM socket for expansion or all the RAM is SODIMM. Other than that, it's all on the system board except the WLAN, the SSD and maybe, the WiFI card. A few, for design reasons rather than repairability, may have small expansion boards for, eg USB and/or Ethernet. Primarily cost-cutting measures in term of manufacture which, to be fair, they ALL do, so to stay competatve, an OEM pretty much has to follow the crowd whether they want to or not. As for parts repair, when new parts are sent out from Lenov, sometimes they are marked up as factory repairs, so those where it's economic to re-work the board, they already do that. I've never seen Dell or HP parts sent out marked as repaired, but maybe they are just less transparent about that.
Having said that, I'm fairly confident they will not be releasing board schematics and/or any board level components as sparers. Consumer repairs will be pretty much as they are now, replace entire modules, eg system board, battery, LCD panel, SSD, keyboard, maybe RAM and not much else, the assumption being that 99% of consumers will have neither the skills nor kit to replace a broken USB port on a system board. That will remain the job of repair centres. On the other hand, if we are going back to easily replaceable batteries in their phones and tablets, that's good news :-)