DMA.LIB bug in DC 10.44?

When I tried to use DMA for an external circuit connected to the AUX I/O (ports A and B) I used the DMAmem2ioe () function (transfer from memory to external I/O) but to no avail.
I traced the library function and found out that the DMA_DEST_IOE bit in the control flag wasn’t set. Setting the bit, every thing worked as I expected. Same is valied to the DMAmem2ioi () function.
Bug or feature?