One cons I did not mention is that it makes the style inconsistent at time, with odd rounding here and there.
With option 2 we wouldn’t have this issue as all existing rounded corners would be updated to the right size (well, only for the themes using the default radius values I agree).

I think this section can be improved or transformed into a bigger section expressed something like: “code for all color themes” or “code for all the design system parameters” with the explanation that basically when you code something, you need to take into account that it may run in different conditions than the ones that you’re looking at (color-wise, size-wise, etc).
If you want to improve just that phrase, it should be “don’t hard code colors or sizes - use Bootstrap & Color theme variables”. It may be that this doc was written before Flamingo color themes, and back then color theme only had color vars, not size vars.
I have opened a separate discussion for this part CSS Best Practive - Generalize on hardcoding rule