smaller surface area and isn't going to flex as much. I wouldn't expect to see a false positive in the case of a bump failure or memory failure. Not from the heat generated by a hair drier. Maybe a reflow, but not the heat trick.
...And this is where the real bad guy of the movie appears and makes his laughing scene... And he is ugly
Of course I can only speculate because it's almost impossible to isolate these problems. But relatively small temperature deltas can very well alter the behavior of the funny chips. I'm talking under 100c. Totally in the range of hairdryer tricks, fake tokin fixes, "overheating"... TOWEL tricks...
Why exactly? I don't know. As you say the area is small. But it's still complex.
Maybe the funny underfill slightly expands/contracts enough to reconnect a precarious contact (also acknowledged as problematic design/material) that was almost there. Removing gpu heatsink, overheating the gpu, next boot it works. Or the opposite. (Console seems to boot fine, but after a certain temperature, problems start manifesting rather predictably... (No hair dryers, all within operating temperature ranges)
Machines sitting unused for years even new in a box, opened and they have problems too. Maybe funny underfill absorbs moisture over time, deforming.
Reballed systems with new lead balls that work initially but fail again shortly after. Where heating them up a bit again also makes difference. Or even pressing down on them.
Now make no mistake, I am not against reballing; almost always there is the alternative explanation.
Mechanical reconnection of balls due to warping of the board...
Progressive oxidation and deterioration of broken balls, oxidized pads that still are barely good but become a problem over time... I have even seen these with my own eyes. Needing to scratch with knife to make the pad shiny again.
Fine working machines that get dropped or physically abused, start artfacting after the fall.
Why artifacting? Why didn't the balls under the CPU break from the fall instead always under the RSX? -Because the balls under the RSX are normally always precarious too, waiting for the smallest chance to break!
And why? I have only lousy explanations such as the wider thermal operation range of the RSX multiplying the thermal cycles, the clamp that only has 2 diagonal screws or the constitution of the board...
But it just happens. Reballing can be the solution many times.
Not always enough though. (ask botakompong)
I wish I could know the real ratio between them. I guess nobody can. But I am sure none of them is zero nor 100.