I am currently working on a corresponding case.
Regarding CAT being '-', I found a similar issue for a MVD report for a multi-volume data set with 30 volumes, where all the volumes up to 20 display CAT 'Y', but for volumes 21-30, a '-' is displayed. Could this be also the case here?
Regarding DSO 'UNK' with no PRI and SEC allocation, please verify the data set Information for such data sets via ISPF 3.4 i. Does this also show similar information like Organization = ? and PRI & SEC = 0 ?