I understand the confusion I think. Separate out the concept of the calibration (device) white from the
adopted (creative) white. So on a DCI projector, ACES adopted white is D60. It will look like D60 even on a
DCI projector. Similarly, on a D65 calibrated monitor, D60sim will give you a D60 adopted white. (it is different than the white point of the device).
So in your example, if you have already graded direct onto a P3 projector with the DCI white, then your grade has a compensation for the greenish white of the projector. In other words, you added some magenta to get a clean neutral. Now if you turn on ACES with these already graded files, the files will show with a magenta correction – the neutral can be graded back to the now ACES D60 adopted white. The equivalent name for a P3DCI Odt is fully a P3D60sim_atDCIcal.
So if you grade using ACES to start, the white point you ‘see’ will look like a D60 white point even if it is on a DCI white projector. You can add any creative white at that point and it will shift away from the adopted white of ACES – the code values will shift to the white point you want. On a DCI projector, the scopes will not show your visual white as being equal. When you hit the edge of the available gamut (i.e. the DCI white P3 gamut), you may see some clipping. This clipping if is it on a neutral will look like the native greenish white of the projector.
The “I render but the WP shift” is where you go astray. ACES is rendered with a D60 system white assumption always. This is always present but the neutral axis is changed for the output ODT in some D65 ODTs (i.e. the non-sim ones) The question of what white is the device calibrated to determines what code values have to be sent to the projector and the calibration white point is where the R G and B will be equal. But the ODT handles that math.
So back to the grade, if you grade to a ‘shifted’ white, like the D65 adopted whites, when you go over to a DCI projector, the grade may turn out to look a little bit warmer and the amount of that is the distance between D60 and D65. (DCI white doesn’t enter into it, because it is only a calibration white point - what code values produce what color).
The adopted system white of D60 is a center point with respect to the grade, but you can take any creative choice and grade to there and that change will be preserved. If you turn off ACES and look at it on a DCI white projector, then it will look greenish white because the equal code values of ACES are now at the DCI white and not D60 where they belong and were designed for.
Hope this helps…