Under QLD conditions, many avocadoes die from phytophthora. Its a massive problem here, so having clonal rootstocks makes good sense, especially if you are a farmer, who cant afford to have half their orchard decline or die after a good wet season. Its common for farmers to drill holes in the trunk to inject phosacid, but even then, you have to continue to inject regularly as you can never get rid of it. So clonal rootstocks that are near resistant to the problem is massive for farmers and will hopefully also help backyarders, who generally struggle with the same problem. Then we'd just have to worry about the fruit spotting bugs, which leave little stones in the fruit flesh...
And yes, the nursery is very professional. You have to give your shoes copper baths when entering growing areas. They are not interested in online business and are already super busy with their current wholesale business. The thing about selling direct is that you might spend the same amount of time dealing with a single customer that only wants one tree (but has common internet neuroses) as you would selling 1000 trees to a few big professional nurseries, farmers or big box stores. They only sell direct once a year at the big plant expo 10km up the road from them, and even there they just take what they want to and wont reveal what they are taking until they turn up.