Welcome to the forum, George! That’s a pretty impressive claim. Was that without any protection at all? I’d love to see what the base of the tree looks like, since my plants that survived even much milder temperatures are all regrowing from near ground level or even below, so you can see the dead stalk next to the new growth, like this:
Out of ~30 outside, it seems like I’ve got about 13 survivors, with only 8-9 of those growing vigorously. None of them had their stems survive more than a few inches above ground level. The Hass seedlings died entirely, the Mexican-race seedlings survived at around 50% rate. Only 1 out of 3 Lula (West Indies avocado) seedling rootstocks survived, and those were all about 4 years old. The survivor lost its graft, though.