When Inga arrives, Klinger tells her that it takes two doctors to sign the Section 8 forms and that he's short 2 doctors. Hawkeye and BJ could sign those forms (in fact, Hawkeye signed several) so this would not be a problem. In earlier episodes, it always took 3 doctors to sign, so with Hawkeye and Trapper John having signed, it still required Henry or Frank to sign. Now, with only 2 doctors needed, the need for Inga to sign is gone.