Hi I made you two screenshots from Nuke. I hope this explains your question.
One is the from a standard Nuke reading a EXR file with a red color 0.5/0.0/0.0 viewed through the sRGB viewer.
The other is from Nuke with OCIO, loading the same file and “interpret” them in two different ways - then view them through an ACES/Rec.709 viewer. Please see the color values in the viewer.
If your 3D software is set to OCIO, the you load the EXR to ACEScg, if your render pipeline is set to the old way (which is now called in MAYA linear sRGB/Rec709), the your load the file as linear_sRGB.