Tested with 3.2.2 and Premiere 26.2.2
We discussed this a bit a few months ago in the old HDR guide thread, but ultimately I moved past it because we were able to get Premiere's native HDR support working in VoukoderPro which solved the main issue I was having at the time, but it's still a bug that the color space, primaries, and transfer function settings in the input node don't seem to have any effect whatsoever:
While most people would never need this, those settings should be there to fix an issue when the editor potentially sends the wrong metadata about those aspects of the video. Note: I have also tried to accomplish this with both the SETPARAMS and SCALE video filters, and it seems to ignore the values there as well. In all cases, it's outputting whatever the editor is flagging the video as.
The only way I can accomplish this is if the ENCODER itself has a way to flag these values, which for example is the case with x265, but as far as I can tell, this isn't possible with NVENC or most encoders. EDIT: x265 will work doing this, but if you select MKV, it will add the original colorspace flags to the container as well, although these can be stripped with mkvmerge header editor
I personally have one specific use case as well where I'd like to make use of this. If I've edited in HDR, but I have a LUT that performs an SDR color grade based on the HDR code values, then technically, once I've applied my LUT, the values being outputted are actually representative of rec709 SDR values, even though Premiere would still be transmitting the HDR metadata. If I could apply my LUT, and then tell VoukoderPro to treat the incoming signal as SDR without having Premiere do any of its automatic color conversions, then I could very easily export the SDR version of my HDR edits with any encoder, without needing to re-interpret all of my footage and create an SDR timeline to handle that. This is especially important if I've made use of specific HDR compositing in my edit.
Just in case you ask, no you can't simply set the connector to rec709, because doing so will cause Premiere to make its own HDR-to-SDR color conversions, which would be incompatible with the already LUT-converted values. I specifically want to take what the editor is sending VoukoderPro, and tell it that no, those reported input formats are incorrect, and tell it the ones I want to use instead.