Dear Aitor,
For YawBrTDzp, a portion of the deflection will come from the transverse deflection (e.g. YawBrTDxt) projected on the moving zp axis, which does not happen with YawBrTDzt.
If I recall, outputs YawBrRVxp, YawBrRVyp, YawBrRVzp were added out of necessity for a project we were using FAST for, but I agree that it is odd that YawBrTVxp, YawBrTVyp, YawBrTVzp were not added at the same time. These would not be too difficult to add through a small modification to the FAST source code.
Best regards,