Is a DTP mandatory in order to load into Write-optimized DSO ?

I'm wondering if a DTP is mandatory in order to load data into a WO-DSO.

Reason: in BI7 i have a 3.x load process of order item data:

2LIS_11_VAITM -> Transfer Rules -> Comm.Area -> Update Rules -> standard ODS.

I now wanted to load the same data from 11_VAITM into a WO-DSO. I actually simply created the WO-DSO using the template of the standard ODS. THis means that the key fields of the WO-DSO are Request#, Datapak-is and Record#. The semantic key is identical to the key used in the standard ODS.

I then created the same Update Rules from the InfoSource goint into the new WO-ODS and last but not least I simply changed the InfoPackaging saying that the data should be now loaded into both the standard ODS and WO-DSO.

2LIS_11_VAITM -> Transfer Rules -> Comm.Area -> Update Rules -> standard ODS

|-> Update Rules -> WO-DSO

What happened is quite annoying and nor understandable right now. Using this process I always get only one record into the new WO-DSO (it's always the first record of the data flow), not more. The PSA clearly shows me all the records with different record-numbers per request/datapak, therefore the key elements of the WO-DSO are clearly unique.

However, as there is always only one record appearing the new WO-ODS, I'm really wondering if the overall process isn't correct at all and that I actually need a DTP to load into WO-DSOs.

Am I right or are there other ideas related to my problem ?

Thanks