Hello,
Yes this is true. - You may also find this tutorial useful for troubleshooting the inheritance:
Troubleshooting DotNetNuke SkinsIf you look in this file at the root of your installation: Default.aspx.vb
this file sets up the page, so you maybe able to trace the procedures that are called for setting the modules css.
Your other option would be to edit the modules CSS and would probably be a better solution, ie. delete the code from the module.css file that is causing the problem.