Those tree’s look very beautiful. But like others mentioned i see some downsides. But every pruning method/tree shape has pro’s and con’s. I think it depends on your situation/wishes which one matches your desires best.
For me the biggest downside here:
-Is that you are somewhat working against the nature of how a tree grows.
I have a few books on pruning. I can’t find the exact passage. But there are some “pruning rules” (remember that those rules here are an approximation. so braking them is fine. But you want to understand the basis behind the rule before doing so)
one of the “rules” this tree form “brakes”
is to
-not let (limb) branch angle go below horizontal. Or not let the growing tip (end) of the branch go below any other part of it. And thus loosing the apical dominance of that growing end of that branche.
The basis behind this “rule” has to do with vigor. A lot of things control the vigor of growing points on a tree. But generally higher up means more vigor. Thus by bending down limb branches past down the horizontal. The tip of the branch is below a lot of the rest of the branch. And since the higher parts of that branch then get more vigor. You will likely get a lot of strong vertical growth on those points (some-times called water sprouts). And very little extension growth on the tip of the branch.
This leads to a high need for a lot of (summer) pruning. And also makes it harder to extend or replace thicker branches. Since the vigor goes to the water sprouts on the highest part of the arching branch. And not to the end.
Once limbs get older. They tend to have less viable/active buds. And i think you will get less water sprouts at the hight points of the arching branches. However if you get increased vigor from a lack of fruit (night frost, biannual harvest etc) you might be amazed by the amount of strong vertical growth at the tops of the arch of the branches you have to deal with.
TLDR
in my opinion this tree form has
Disadvantage.
-going against natural tendency of a tree to grow upwards, leads to vigor on places where it isn’t desired. (highest point of the branche=middle of arch and not end of branch)
-this leads to a high need for pruning strong vertical growth. likely summer + winter pruning needed.
-not the most efficient space use. If you think of the shadow this tree has. It is probably donut shaped. (leaves /fruit are in a ring on the outside of the tree, with a hole near the center that is largely leaf-less) And thus it doesn’t catch sunlight near the center of the tree.
Advantages.
-because the “high vigor” zone is at the top of the arching branches and not the end. you lower vigor at the end, usually leading to more small (fruiting) wood at that spot.
-the “fruiting zone” is nice and low on the outside of the tree. Easily reachable.
-it looks very beautiful.
This is just my (relatively informed) opinion not fact. I don’t claim to have more expertise than Paul Gautschi or others.