I am not sure
if the advice in the HIG applies to this, as it is (or should be) fairly
obvious that changing to a different theme will affect options not shown
on the current tab.
I wouldn't say that's necessarily true, especially as not all the other
tabs (e.g. Options) do comprise the Theme, just some of them. In fact,
at least one of the tabs (Fonts) mixes some things that are part of the
theme (the fonts themselves), and some that aren't (the anti-aliasing
options). I can't help feeling some cleaner separation would be
preferable.