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.)

You basically nailed it. USD crashed in the 1970s after the Nixon shock, and is basically a shambling corpse losing 3-8% of its value every single year while BTC is 600x the value of a 1913 dollar... and trending up: https://i.imgur.com/PJT01T8.png

Even if they don't give me a raise, I'll still have more purchasing power at the end of a year rather than less as the case with USD.