Meta Boxes always appear on Pages and Posts regardless of the 'pages' setting. Will never appear on custom post types.
The 'pages' setting doesn't survive Easy_CF::parse_field_data() - where it is excluded from the construction of Easy_CF::_field_data. Since that array key is not set the default setting for 'pages' is used in Easy_CF::add_meta_box()
add the 'pages' element to Easy_CF::_field_data.
'pages' => $group_data['pages'],
to line 570 of easy-custom-fields.php (in Easy_CF::parse_field_data() )