Is it necessary to fill out supplemental V2011B if I am traveling on a 12 day tour?

You don't need to fill out supplementary Visa Application Form V.2011B if you travel to China on a 12 days tour and apply for China tourist visa in USA.

For work visa \study visa applicants, or if someone else travelling with you shares the same passport with you, or if you are applying for a visa in a country or territory other than the country of your nationality, a supplementary "Visa Application Form of the People's Republic of China" (Form V.2011B) is required.