This really is the crux of the matter. The Apple Authorized Service Providers don't actually FIX a problem, they REPLACE the problem. So the people who have the desire, and ability, to repair things like logicboards, have to stumble around and figure out the solution on their own because Apple will not provide the schematic to them. I would feel much better about buying these "non-repairable" computers if more people were actually able to repair them versus just replacing the whole logic board. There are plenty of shops (and private people) who have the skill and equipment to do this if they just had the information.I am not sure you get it. Miniaturization doesn't matter. The problem is Apple does not share documentation. It is much harder to diagnose and repair anything when Apple makes it a puzzle.
With documentation, independent repair shops can fix many problems that Apple won't or won't do economically. For example, my 17" MBP died. Apple quoted me nearly $1000 to repair. I managed to get board and circuit schematics and traced the problem to a tiny surface mounted capacitor. It literally cost me $0.25 to replace it. Just this week Apple quoted my cousin $1200 for a logic board replacement. I traced the problem to liquid damage in the keyboard causing the SMC_ONOFF to short. Literally a $23 repair. Without documentation there is no sane way to trace problems and identify/test/repair. In just two examples here, I showed savings of almost $2200 off what Apple Service quoted simply because I had documentation.
Apple clearly has financial motivation to hinder any means for independent repairs. The irony is that Apple does not even seem to use the documentation that it hates to share. They make no attempt to actually repair faulty parts (they throw them out and install whole new part). And with the trend towards ever more integrated components (i.e. soldered SSDs), it is going to get far more expensive to do repairs with Apple.