I finally managed to track down the code that sets that. /manager/controllers/default/resource/create.class.php on line 105. All of the other options are controlled by a setting except that one. So all I need to do is add a System Setting and clone the other lines:
'richtext' => $this->context->getOption('richtext_default', true, $this->modx->_userConfig),
'hidemenu' => $this->context->getOption('hidemenu_default', 0, $this->modx->_userConfig),
'published' => $this->context->getOption('publish_default', 0, $this->modx->_userConfig),
'searchable' => $this->context->getOption('search_default', 1, $this->modx->_userConfig),
'cacheable' => $this->context->getOption('cache_default', 1, $this->modx->_userConfig),
'syncsite' => $this->context->getOption('syncsite_default', 1, $this->modx->_userConfig),
Works like a champ. Set it to "Yes" in System Settings, and to "No" in a Context's settings, and creating new resources in the context will have it unchecked.