Premiere has issues with missing metadata. It doesn't care if the values are stretched. What happens is that it can infer missing metadata correctly when the values are shifted and zero padded to 16 bits. Also, there is 14-bit CinemaDNG, but Premiere has trouble with 14-bit uncompressed (not with compressed though!). Now that all ML dng is compressed, it should work fine with Premiere at 14 bits.