Again, I never said the problem is with all projectors, I simply said on some JVC's I've calibrated, including my RS-45. And when this problem exists, the posterization isn't about getting the correct 709 primaries and secondaries (even though this requires a Lumagen on the 45 since no CMS), but getting it to the correct positions is often what causes the posterization on some projectors. I have seen it on DLP's too, the Viewsonic Pro8200 is one, though it's very very minor compared to the JVC.
If the problem occurs when you manually do a step, then the auto-cal is usually less-likely to fix it, because auto-cal isn't magic, it's just software modifying things until it gets it right. Though it keeps getting better every year, not sure who has the best auto-cal profiles. I never tried it on a Lumagen.
Zombie10k has done the auto-cals on the JVC RS-55, you can ask him.
I'm saying the limitation is an inherent hardware or firmware fault to the way the color table is interpreted. cannot fix it with auto-cal, but no idea if it applies to the newer JVC's.