The cool band in dark end of greyscale gradient.
Also bothering me: when switching to Monitor RGB proof view in PS (so the monitor's profile is not used), the gradient doesn't really change - it is still smooth with the single green band. I expected it to look awful without the profile - or at least different.
Switching a monitor profile in general shouldn't change a thing in grayscale rendition except for gamma differences. Since most profiles have 2.2 gamma, you should never see a change in grayscale gradients.
Selecting a monitor profile for proofing purposes in PS is just selecting an intermediate step in colorconversion, your monitor profile will still be used to display the final result. It is however useful to see what happens if your carefully created wide-gamut image will be converted/displayed as sRGB. It is not useful to see what the effect is of different monitor profiles in a workflow, because videoluts aren't applied or changed when proofing monitor profiles.
The cool band is a point of concern:
Try white = native, and black = native
if that doesn't remove the band, then there is reason to contact the manufacturer, or perhaps Basiccolor.
if it does remove the band, then you could try to gradually lower the white target from native to where you start to get the band. Then see if that potentially high whitepoint is comfortable to look at.
(The native white point could be in the 9000K range.)
Remember, for your situation, once your eyes/brain adapt to the new look, it will not affect your workflow since there is no outside reference. That is: there should be no outside reference. If your workenvironment includes windows where you can see clouds, or get diffuse outside light, then you might have a problem. But even then, only if part of your workflow involves "eyeballing" correction. That is: if you are requested to make an image look "warmer" and you don't do these sort of corrections by the numbers, then you obviously need some kind of universal and consistent reference. You can't do that consistently if you keep adapting your eyes to different whitepoints.
However, it is far more important to have some form of reference graybalance at capture time, than during viewing. For example, if you have a graycard in some of the captures of a capture session, it allows you to set the graybalance of all the images correctly, and hence you know that the images are correct. Your eyes will adapt while viewing the monitor, so that is not too much of a problem. Just make sure that it is consistent.
As a side note:
1. a consistent whitepoint to me means your whitepoint is the same each time you use your computer,
2. a reference whitepoint to me means your whitepoint is the same as some outside reference which include for example a viewing booth, or UK daylight.
In your case, a consistent whitepoint is more important than a reference whitepoint.