From what I've gathered by following the issue (weird fascination really, not a launch buyer), the choice (and ability?) to go smaller and no power brick, doesn't seem to have anything to do with the failing units.
It's not a standard issue of overheating or something, it seems to be faulty batches with various issues, such as the HDMI connector, the fans not working (which obviously leads to overheating but not because of the console design), etc.
It's probably more a case of rushing for all these pre-orders/ a choice for cheaper manufacturing process/ manufacturers hiding the issues, or something similar.
I could also be more wrong than a gaming press journalist talking about the insignificance or resolution in games.