New Mac OS Brightness Slider for External Display in HDR mode only? Blown-out picture?

Before diving into the issue, I want to clarify "brightness" vs "backlight" of the display. These are often used interchangeably by manufacturers and can be really confusing. Brightness is often used to adjust the backlight of a display (like a dimmer switch) and other times, it's affecting the picture itself, not just the luminance of the display.

When using Apple's built-in display, the brightness setting only controls the backlight of the display (as far as I can tell).

When using an external 3rd-party monitor, this brightness slider was previously disabled entirely (which I actually prefer). Although this doesn't seem to be the case any longer.

I use an external Samsung HDR display connected to an M1 Macbook Pro for my main/only dispaly. In "normal" SDR use, this brightness slider is still greyed out. However, when I enable HDR in system settings, the brightness slider appears, but it seems to be affecting the whole picture itself, not just the backlight.

This actually makes sense to me, as I don't see how Mac OS could alter the backlight of a 3rd-party monitor, but it can alter the image being sent to this display.

My backlight on the display is set to 100 (for HDR content) and this value doesn't change with the Mac OS system brightness setting (as expected).

I recently noticed that highlights were really blown out when viewing HDR content on the Samung display, which wasn't an issue on this same setup in the past... If I lower the brightness from the system settings, it seems to affect the white-point and peak brightness of the image all at once. The problem is, to get the peak whites low enough to not clip, the rest of the image is much darker, and I'm not sure the highlights are as bright as they're supposed to be anymore...

I can't help but think this is supposed to be a feature not a bug, but if it is intentional, the implementation doesn't seem right. Anything over 50% brightness starts to clip badly (see pictures).

It doesnt seem like the latest Mac OS is capable of displaying a "correct" HDR picture anymore? At least on my setup. I'm only watching content, but this could be a real problem for someone trying to edit or create HDR content.

Anyone else notice any issues with this? Sorry the pictures aren't great, but you can see what I'm talking about.