The density is different between Windows and Mac even with the same monitor. The UI on Windows is much bigger.

The UI scale on desktop depends only on the system scale. This system scale usually isn't set the same way as is it set on mobile devices where it is adapted the density of the screen (to look the same across devices). It may look bigger on Windows in your configuration either because the UI scale is larger comparing to macOS, or monitor's density is lower. The same difference should be visible on usual web sites in browsers.