Clarification question regarding `last_frame`

The standard states here:

Member last_frame is set to SANE_TRUE if and only if the frame that is currently being acquired (or the frame that will be acquired next if there is no current frame) is the last frame of a multi frame image (e.g., the current frame is the blue component of a red, green, blue image).

This sounds to me as if the following is true:

Whenever format is set to SANE_FRAME_GRAY or SANE_FRAME_RGB, last_frame should be equal to SANE_False.

Is this interpretation correct?

• If yes, then this aspect is not correctly implemented in scanimage, which would be a separate issue. In that case, I would suggest adding the following line to the standard, since I doubt that the implementation is conistent across all backends:

  "In particular, the frontend should ignore the value of last_frame when format is set to SANE_FRAME_GRAY or SANE_FRAME_RGB."

• If no, then I would appreciate a brief explanation and come up with a suggestion for the formulation afterwards.

Kind regards and thanks in advance!