If you are going to quote the INS website, you need to quote it in context.
A14 on the INS website (I assume this is where you got your quote) states:
"Finally, AC21 gives extensions of H-1B status in one-year increments to H-1B aliens who have an employment-based immigrant visa petition or application for adjustment of status pending if It has been more than 365 days since the visa petition or the labor certification application has been filed. Note that the adjustment application, labor certification, or visa petition need
not necessarily have been pending for a year to obtain this benefit. The only requirement is that 365 days have passed since filing of the labor certification or immigrant visa petition."
This states that you need to have an employment-based immigrant petition (an I-140) or application for adjustment of status (I-485) pending. I do not understand why people insist that the law is ambiguous. It seems pretty clear to me as soon as you realize that a LC is NOT an employment-based immigrant visa petition (look at the top of form I-140).