Aha so by depending on it transitively I also inherit whatever possible changes have happened to it, despite having explicitly declared 1.2.1 as my normal compose dependency, good to know.
And this isn't a problem about accompanist, as that one nicely has a stable and a beta/alpha release which depends on the correct compose version, so that's good (currently latest stable 0.25.1 depends on latest stable compose 1.2.1). But the MDC one doesn't, so that we will then have to hold back from bumping due to this, just to be on the safe side.
Also as a side note, it doesn't give me much confidence that the MDC lib is a standalone lib outside of androidx and even accompanist. Makes me wonder whether I should bite the bullet and simply define my MaterialTheme myself making sure I set each value the same as it is in the XML files and simply keep track of having them in sync myself.