You are technically correct, the best kind of correct!
The differences are very subtle though and unless you also flag for bt.709, bt.601, etc, you still won't know how to interpret it accurately.
If we get any one of the above, at least video would be feasible.
Decoders still can output ARGB32 video, in fact this format is required for decoder output. Other common format can be selected using MMA_UseBestFormat tag. In this mode, decoder try to decode image with nearest common format available. For example, for 8bit jpeg data it outputs normally ARGB32 but with this tag, user can ask decoder about output format for given image and process it directly as gray8.