I have never used the DNG converter in the manner you are suggesting. However, I just tried converting 2 16-bit TIF images to 8-bit TIF images, And then tried converting them with the DNG converter. The converter didn't seem to like the images, and the conversion didn't take place. Have you converted 8 bit TIF images before using the DNG converter? I'm just curious to know.
I have not used it before to convert 8-bit Tiffs.
I am only assuming it does so, because the program pulls the tiff files into the cue when you have them in the folder you are converting.
When the program goes to convert them (16 bit tiffs) it gives me a status of ...
"there was an error parsing the file"
Perhaps I am incorrect in assuming the results would be different with an 8 bit Tiff.
I got the same error on the 8-bit TIF files that I just tried to convert. Incidentally, Photoshop is one program that will convert from 16-bit to 8-bit.