with that much detail in the sculpt , I'd expect there to be quite a difference so there's got to be something else going on. might be worth uploading some pictures of the bakes / renders
Here are the displacement bakes out of ZBrush (just the head again for the UDIM one.) Original files were 32-bit exr format and red color, I've desaturated them to be easier on the eyes. Something else strange - on my duplicate model with only 1 tile, it showed like 90% of the displacement without any subdivisions turned…