First, do you have the following in your _output.yml file?
bookdown::pdf_book:
includes:
in_header: preamble.tex
If not, you need it, otherwise the preamble.tex file will be ignored.
Second, I don't know latex at all, so I can't remember whether this matters, but in my preamble.tex I have that code just before this line:
\makeatother
Now, to the actual answer to your question. I thought you could just do it the way you already had. I'm 99% sure that used to work, but I just checked my book, and it wasn't working in my PDF either! So I managed to track down the problem. You just need to slightly modify your RMD to be like this instead:
::: {.rmd-details data-latex=""}
text goes here!
:::
Let me know if that fixes it.