I believe I have found the fundemental difference. whilst H.264, jpg and exr export DO embed the profile set in output module, prores and dnxhd format does not embed - and so the files are exported as rec709 format.
if I bring the render back into the same project and convert it to sRGB it matches.
With that understanding if I knew i was to export in this format I could setup the project in rec709 to begin with but it really should not be the case should it???
whats more, why does it react differently when rendered through Media Encoder. the files still come back in as rec709 but the color matches.(there is the tinest of changes on the lumetri scope but its a visual match.)