Hi Juraj,
Your findings allign with the SAP Help documentations.
Below is the 2 links which are served by SAP for EHP4. It seems like SAP decided to convert existing Web Dynpro screens to SAP UI5.
They have already started to perform this activity with SCM - APO's replacement tool as SAP IBP.
Here is the link referenced to SNC EHP4 technical changes:
Overview Link:
Details Link:
I did not have the chance yet to work on EHP4 but i will appreciate if you let us know if you different findings.
Regards,
Selim Batur