That doesn't follow. I'm pretty sure they're talking about the effect of nominal wage stickiness: you're not constantly renegotiating your rate, so when there's fluctuations in relative value, it matters what unit the original number is denominated in. Compare with the case of a US expat being paid a steady salary in USD and converting to the local currency to make purchases, if you want an example with a similar mechanic but very different intuitive feel and practicalities.

(I'm not sure they're right about the overall effect though.)