output_theme and the timing of config file merging

[Nick Moffitt]

http://intertwingly.net/code/venus/docs/config.html says:
> output_theme
>     Directory containing a config.ini file which is merged with this
>     one. This is typically used to specify templating and bill of
>     material information.

Does this merging happen only during HTML generation, or does it affect
spidering as well?  That is, could I set (say) spider_threads in two
different themes and have that setting affect all sites and configs that
use them?

If so, can I rely on this behavior?

-- 
"These people program the way Victorians dress.              Nick Moffitt
It takes two hours and three assistants to put on           nick at zork.net
your clothes, and you have to change before dinner.
But everything is modular."    -- Miles Nordin, on PAM