The Windows HiDPI behavior (on my system with a screen scale of 1.25) with a policy of NEXT or LAST, the divider tracks the mouse cursor as expected.

With a policy of FLEX_NEXT or FLEX_LAST, it tracks until the first (or last) column being resized hits its minimum and it switches to another column. Similarly, with a policy of SUBSEQUENT, it doesn't quite track as expected when one of the columns gets small (i.e., close to its minimum). This might just be error accumulation. It seems like a minor problem.

The issue can be reproduced on Windows by setting fractional scale:

Windows 11:
Settings -> System -> Display -> Scale -> 125% (or 225% ...)

Please refer to the attached video clips. At scale 1.0, the cursor tracks the divider. At scale 1.25, the courser decouples from the divider at some point.