I am not sure I quite follow the thinking.

If something has zero intrinsic value, does it matter which units are used to expressed that (so long as the units themselves have some non-zero value)?

Are you sure that US Dollar or Gold or bread have some intrinsic value? Day to day they do have some stable price but on a longer time scale that changes a lot.

Let's take EURUSD for example - both currencies are loosing purchasing power but EUSUSD ranges from 0,9 to 1,6 within last 50 years.

In some sci-fi scenario US Dollar could also go to zero if for example USA looses major war with China as is left with crushing debt. This is a possibility. What would be the value of Bitcoin then?

If USD became worthless, people would stop denominating the value of bitcoin in USD. This (or less drastic but still major fluctuations of USD) would complicate questions about how bitcoin's value had changed over time, but I'm not seeing how it would create ambiguity over whether bitcoin had 'gone to zero' or not.

What does "intrinsic value" mean?

Why would it have value in relation to some of those and not others? Sure, state action could make it hard to exchange bitcoins for other currencies, but we could still infer a $ value by looking at the btc and $ prices of goods they can both buy. (And yeah there can be complications and imperfections in that process, but not enough to make the statements 'bitcoin does/doesn't have 0 value' particularly vague or ambiguous.)