why do you feel the need to share your opinion about technology you clearly do not understand?
1) 1 billion colors refers to quantization of colors, not how vivid those colors are. this has no relation to color gamut only the bit depth of the display technology
2) most apple displays are actually still 8 bit, so in reality they can cleanly output only 16 million colors. 10 bit refers to 10 bit like presentation in gradients where the low levels of quantizations are apparent. apple achieves this with dithering
3) you cant tell the difference because you dont know what your looking for, you dont know where its noticeable (p3 red is much better than srgb while blue is similar), and probably dont even know which content is taking advantage of it, because most stuff is still mastered for srgb.