How do Windows and Mac OS differ in how they handle HDR?
Yes, they do.
When HDR is enabled on Windows 10 or Windows 11, the standard profile is disabled and an advanced profile is used for the display profile. Spyder X Pro and Spyder X2 software create a standard profile.
When HDR is enabled on macOS it does not change the display profile. HDR is only enabled when HDR content is being shown on the display.