Warning: The file format reports no CFA pattern for the master dark frame?

[rockyraccoon]

I'm trying to dabble with processing DSLR (Nikon D7000) images in PixInsight
I've checked these boxes the DSLR_RAW preferences in format explorer:
create raw Bayer CFA image
no black compensation

I've then acquired the following calibration frames:

bias
darks of the same duration of lights (30s)
flats (.5s duration)
darks of the same duration of flats

I wanted to calibrate 330 x 30s subs

If I feed the whole thing in BPP (in groups of ~50 lights at a time so as not hit the known "too many open files" problem), I get this warning message:


** Warning: The file format reports no CFA pattern for the master dark frame, but it is being forced as per process instance parameters.

the script proceeds to produce master frames that I don't if I can trust (given the warning message).

Why the warning?


As I'm used to deal with frames generated by a dedicated astro CCD, I can't say if the master frames  look "right".
I'm attaching links to the master frames to seek opinions.


bias:
https://drive.google.com/file/d/0BxXnXrObbkzlMDRiWEpWdG1lSTQ/view?usp=sharing
flat:
https://drive.google.com/file/d/0BxXnXrObbkzlaFNUTkpXQnpOZnc/view?usp=sharing
dark (30s):
https://drive.google.com/file/d/0BxXnXrObbkzlaFNUTkpXQnpOZnc/view?usp=sharing
dark (.5s):
https://drive.google.com/file/d/0BxXnXrObbkzlUWZsTVdoZEItOFk/view?usp=sharing

Thanks in advance for your input!