Problem with a seedling, of course, is that it will not be true to type. One of the nurseries sells macadamia trees thru HD that carry a label identifying the tree as a "Cate". On the reverse of the tag it is identified as a seedling. I thought we were past this selling seedlings as a specific identifiable, predictable genetic type. Given 10 years looking at a "Cate" seedling production and that of a true grafted or airlayered CATE, would lead to inevitable differences. Growers need predictable outcomes, especially after an investment of time and $. Ten years from planting the seedling's crop could just be junk. Difficult enough differences caused by climate, soil, water quality, etc. A seedling is a seedling, nothing more. May be better, may be worse than parent(s). To expect a specific outcome from a seedling's variability is unreasonable, and most people know that. So do the nurseries.
Of the 50 or so macadamias I raise, about a half are seedlings of unknown parentage. Many, if not most, produce excellent nuts. Some, not. Of the 14 named varieties, grafted, nut quality corresponds with known standards. I don't think we should expect anything less.
Seedling trees graft easily as long as the scionwood is girdled about 3-4 months before cutting. Results are close to 100%.