Why do you question the claim?
The power consumption doesn't scale between the two by the quanta of miners, it scales differently because the algorithms are different and thus the power consumed is different.
I have no idea how the algorithms differ nor how the difficulty differs among the two, so I don't have an intuition about how to guess whether or not they should scale relative to each other. I suspect that ethereum's market cap would be lower and probably have lower mining rewards therefore less capital invested in its global mining pool. I suspect that ethereum's algorithm requires more energy per block than bitcoin's, but I have a hard time guessing how much. Especially since it's a little less mature, maybe fewer ASIC miners so even less efficient in practice.