L Visa requires a Lettrer of Duty Authorized Unit Form?

Hi,
(Chinese Embassy in Delhi, India)

My fiancé had all the appropriate documents for the L type but the counsular said that he needed a form (invitation Letter of Duly Authorized Unit) that is only for M, F, Z types and work permits.

We called the embassy 2 months earlier and they never mentioned this form for his L type. My company (Chinese) also said that they've never heard of it and that it does not apply to an L type.
Is there any reason why the Indian embassy demands this form when it is not listed as a requirement?
Thank you!