This is a complex topic. Note: you would get better results using standard instead of raw. Now when using filmic around 0.69782 is 50% grey on Linux mint cinnamon DE. I’m not sure if it’s the same on other OSes. So some things to consider.
1. You have the gradient texture. Linear(I think ease gives better results). Then It’s processed by a color ramp. Are you using fac or color output of gradient node? They produce different results when passed through the color ramp. Then there’s the processing of the color ramp. Ease gives better results than linear.
2. This then gets processed by the shader node which takes into account global lighting and light objects.
3. Then you have color management which then adjust the colors.
4. Then there’s the display/monitor processing. I mention this because you brought up Photoshop and “true” gradient. Photoshop’s color management uses a color profile bases on your video card and display. On top of that it has a gamma correction that is set when you install Photoshop. So it’s not a true gradient. it’s a gradient that has been calibrated to your specific GPU and display/monitor. Blender on the other hand uses a straight display/monitor color profile.(by default it’s sRGB)
