What version of test code did you use in tpl_main_page.php? (Paste it here.)
You can extend or alter that test to fit the category and product info pages as well.

Since the homepage and category pages are all "index" page base, you can use something like
PHP Code:
if ($current_page_base == 'index' or $current_page_base == 'product_info') {
  $flag_disable_left = true;
}