[jiggawatts]

It is common-place-ish.

Windows since Vista can use 16-bit float buffers for the desktop manager. Some applications support this too for all controls and UI elements. Desktop graphics applications support 10-bit, such as Photoshop. Similarly, video playback is generally 10-bit.

In the past, this feature was reserved for the ludicrously expensive "professional" GPUs like the Quadro series, but it has been enabled in software for the mainstream AMD and NVIDIA GPUs. Very recently (just months ago?) my Intel GPU gained 10-bit output capability even in SDR mode.

It definitely works, I used "test pattern" videos and test images in Photoshop, and even dark grey-to-grey gradients are silky smooth on two of my monitors. This includes a 7-year-old Dell monitor!