This seems to be unrelated to Z-offset, as it’s happens regardless of print placement and orientation but follows infill direction with the more squished part being towards the end of the layer and the slightly less squished part being the beginning.

This should not be the case. You shouldn’t have too much material at the end of a layer and too little at the start (or vise versa). Does the result look the exact same no matter where on the bed you put it? Like it looks the same centered vs put in corners but keeping the same orientation and print order.

If it happens anywhere on the bed in the exact same way then I don’t think it is a bed mesh problem and wondering if there is some sort of e-step problem that is compounding over the course of the layer, but resets on a layer change. Maybe try relative positions vs absolute positions in the gcode settings to see if it changes anything?

However, if moving the print to a different part of the bed moved the “problem areas” then there is either a motion system issue or bed mesh issue. Something could be out of square, or a z-axis lead screw is out of shape, or even I’ve seen printer firmware just tossing out the bed meshes - they will still scan them, but then just tosses it out at the beginning of a print (could be problematic “beginning gcode” in the slicer doing that too).