I’m using Dynamic Data to set the Transition value under Theme Style > Button > Transition. It does not render the ACF value in the CSS, instead just {acf_transition} (creating broken cSS). I have tried multiple times. Same issue. If I output {acf_transition} in a Heading or somewhere else it work
EDIT: Actually I think the issue might be more that it’s offering a Dynamic Data selector on the right of this field, rather than the Global CSS Variables option that Transition fields have in other places in the site. I have skipped using ACF now and instead I’m manually entering a css var() here from my global variables.
I’m quite surprised that no one has ever reported this before (and that none of us have noticed it) The dynamic data picker is superfluous in this setting. As you say yourself, the variable picker would make much more sense