VA decoders implementation has been verified during 1.18 and 1.20 development cycle and also via the Fluster test framework. Similar to other cases, we can prefer hardware over software in most cases. As in D3D11/DXVA codecs, MPEG2 is hold as secondary since it still needs more validations.
At the same time, all GStreamer-VAAPI decoders are demoted to NONE to avoid collisions, beside with vaapisink. The first step to their deprecation.