b2 application in chengdu

My parents visited us last March. They got 6 months' stay. Then I extended another 6 months for them,But they left in Dec..

Now I would like to invite them again. The following is what I got from US Consulate in Chengdu
"Applicants applying for a B-1 (business) or B-2 (tourist/visitor) visa may drop off their visa applications at the U.S. Consulate in Chengdu for adjudication and are not required to appear for a visa interview so long as their previous visa is currently valid or expired less than twelve months ago, and they are applying for the same type of visa."

I am not sure if my parents fall into this category so they don't need interview.

I really need your help. Thanks a lot!!!