black and white tint anomaly

I have a conundrum:

I have a series of black and white images that I want to tint just a tiny bit warm. There are many methods — gradient map, solid colour adjustment in colour blend mode, HSB colourized, photo filter.

I have done one or another (tried them all) and then taken the adjustment layer over to another file and dropped it on the new file, assuming that I will end up with the same tint. In order to verify this I have set up a bunch of  color samples and set the info panel to HSB to check the hue angle (I like to use 38 degrees which is a warm yellow/brown). 

In this example I have used a grad map set to hue 38 and 3% saturation, I have plotted swatches so that location 25 is 25% luminosity, 38 hue, 3% sat, then location 50 os 50% luminosity, 38 hue, etc etc.

SO... I'd expect the colour samples to reflect this. What I'd expect to see is that the the readout is H 38, S 3 and that the only value that changes is the brightness depending on whether the colour sample is over a light or dark area. 

What I see is that when I sample a different area of my image the hue varies from approx 30 up to 44!

I just cannot understand how with every swatch on my grad map set to 38 hue I am able to get diffeeing readouts in the info panel.

This same thing occures whatever adjustment layer I use. Photo filter set to 38 hue - same variation of colour samples, HSB colourize set to 38 - same deal. Please someone explain this!!

How do I know my hues are the same in all images if I cannot actually get a reading of 38 on the majrity of my samples??? I have tried varying sized of pixel averaged samples but it makes no difference.

Can someone try this out and tell me they get the same results?

Note the screenshots below - my grad map says hue 38, my colour sample says hue 44... how?

Thanks.