> there is a very real danger to insufficient paste application on a bare die
So, I've repaired and cleaned many, many laptops and computers over the years. For bare die components (CPU/chipset) I use something like "half a grain of rice per finger nail area". This is already plenty. I sometimes checked after mounting, and there was always some minor squeeze-out. (For desktop CPUs I also use just half a grain of rice. The higher mounting force results in about a ~3-4 cm dia circle; this doesn't extend all the way to the corners of the IHS, but it doesn't have to, since nothing is dissipating heat there.)
> there is no real downside to an enthusiastic application of paste except for making a mess
That's not my experience.
With laptops, the pressure applied by the cold plate is not that much and thermal pastes have high viscosity. (The cold plate is often not that stiff, too, so it tends to flex). Applying too much paste results in a too thick layer of paste, which results in higher temps, hotter laptops, fans spinning faster and thus more noise and annoyance.
Indeed often I found the issue with manufacturer-applied paste was that it was simply too much. I think the reason they do this is that it's harder to get wrong and it makes the product just more annoying, not break it. If they did it properly, there would be some chance of getting it wrong, resulting in a broken product. For the same reason they're using thermal pads wherever they can get away with it: They're practically impossible to misapply.