Since people are always asking for “real world examples”, I have to point out this is a great place to use an agent like Claude Code or Codex. Clone the source, have your coding assistant run its /init routine to survey the codebase and get a lay of the land, then turn “thinking” to max and ask it “Do the Blackbody attribute for volumes and the sky generation nodes still expect to be working in linear sRGB? Or do they take advantage of the new ACES 2.0 support? Analyze the codebase, give examples and cite lines of code to support your conclusions.”

The best part: I’m probably wrong to assert that linear sRGB and ACES 2.0 are some sort of binary, but that’s exactly the kind of knowledge a good coding agent will have, and it will likely fold an explanation of the proper mental model into its response.

If you make a color space for a display, the intent is that you can (eventually) get a display which can display all those colors. However, given the shape of the human color gamut, you can't choose three color primaries which form a triangle which precisely contain the human color gamut. With a display color space, you want to pick primaries which live inside the gamut; else you'd be wasting your display on colors that people can't see. For a working space, you want to pick primaries which contain the entire human color gamut, including some colors people can't see (since it can be helpful when rendering to avoid clipping).

Beyond that, ACES isn't just one color space; it's several. ACEScg, for example, uses a linear transfer function, and is useful for rendering applications. A colorist would likely transform ACEScg colors into ACEScc (or something of that ilk) so that the response curves of their coloring tools are closer to what they're used it (i.e. they have a logarithmic response similar to old-fashioned analogue telecine machines).