I believe 10-bit is the amount of colors shown while P3 is the gamut or range of colors that can be shown so it’s not a straight up comparison.
Per Apple their HDR display’s support Dolby Vision, HDR10, and HLG. Dolby Vision and HLG are converted to HDR10 when viewed on other HDR10-compatible external displays.
HDR10 is 10-bit so per Apple it should support it.
Support for high dynamic range (HDR) video, such as HDR movies and TV shows from Apple or other providers, requires the latest version of macOS, a compatible Mac model, and an HDR10-compatible display, TV, or projector.