The thing that pokes holes in the Illusion theory is how adamant the "Illusion" is. I can experience the object, say Yosemite Valley and some one else can also experience it and you can fly a fellow in from Borneo to also experience it and by golly! all the experiences gibe! There may be psychological angles which you pointed out LH (and you called THOSE variances "illusion") and variation in the physical points of view, etc. but the place has a reality (key word there) all it's own. Our "words", which are once removed from reality (all language is metaphor) may cause some consternation but the physical presence cannot be denied. This is why science works! Repeatability of experiments. I have another word for "illusion" if someone holds fast to that concept and denies reality: delusion!