Just because a projector can reproduce 100% of the DCI-P3 color gamut does not mean it can show all the color shades that are found in HDR content. Color volume is the combination of color gamut and brightness range and one of the things that makes HDR look so much better than SDR is its massive amount of color volume. Higher brightness range gives you the ability to reproduce the look of Ferrari red in the shadows and in the sunlight.
Most projectors must sacrifice brightness to deliver a wider color gamut, which reduces the color volume. Many high-end projectors can produce 90% of DCI-P3 without the color filter so why sacrifice over 20% of your brightness to get an extra 10% of coverage? Cinema filters sacrifice brightness in order to produce 100% DCI-P3, which is why Sony 4K SXRD home theater projectors like the VW915ES do not utilize them.