That’s not at all what I was thinking- I was picturing something like a horse who is short-coupled and a rider with quite a long leg who would need either a larger seat or a more forward flap than the horse’s body could accommodate. 
That sort of conformational pairing can require some creative thinking to saddle!
As far as pelvic shape and tilt go, I have been interested to see new saddlers paying more attention to this because it certainly impacts the way that you can use your seat. However, the fact that there are only one or two saddle companies out there who are advertising that they’re paying attention to this suggests to me that what everyone else is doing- width of twist, width of seat, length of working center, placement of stirrup bars- is already addressing the matter. My own experience is that the fall of my leg against the horse, and my ability to use my hips and seat, were better improved by 6 months of yoga, hip mobility work, core muscle development, and rolling my tight left psoas on a tennis ball than they would have been by buying a saddle that adjusted my rotation for me. This is not to say that ErgoX2 is making a bad saddle or is marketing some nonsense, just that if you do have an issue with pelvic tilt that makes it challenging for you to use your seat effectively, a saddle that allows you to get into the correct position plus doing your musculoskeletal homework so that you can stay in that position will have good odds of solving your problem for you. Mileage is variable on that one.
