Some ISF techs are more familiar with particular brands than others. While setting grayscale is basic, there is more that can be fixed if you know how to fully navigate the service menu.
I made SM adjustments on my Sony that got me very close to a good grayscale, using a #85 photogray card. Under the advice of a very competent tech.
But we also had made adjustments for red push, as well as numerous other tweaks specific to my display, including gamma.
Using Avia, or DVE, is essential to start and finish with. And sometimes as an intermediate step when changing cuts and drives in the service menu, and needing to establish a baseline again, for contrast and brightness.
None of this should be attempted except by the most competent or under their assistance. Arbitrary adjustments in the service menu can render your display useless, or even void your warranty. I think the latter is more of a scare-tactic, but if it keeps the unprepared from venturing into the SM it's effective.