Accuracy of Quantum Chemistry ML models
Yes, you're exactly right - multiple papers in chemistry ML drop the units.

There are even comparisons (usually by statistics, ML or comp. sci. researchers) where models are compared by "averaging" errors down a column like that. Of course that's meaningless, since you can't average electron volts or Hartree (energies), Debye (dipole moments), and volume (polarizabilities).

Worse, energies are often computed as atomization energies - so for large molecules, they can be enormous...

In my opinion, a more relevant and meaningful statistic would be the Mean Absolute Percent Error (MAPE) which is unitless and easier to understand (e.g., 1% error? 0.01% error?)

That said, the original QM9 paper gives the units Table 3:
Scientific Data (2014) 1, art. 140022