There are lots of reasons for either way to be good, depending upon yourself, how you started, how you shoot, what you shoot.
Imagine, shooting barebow or traditional,having the arrow as close to right under your eye as you can get it is a plus. You can aim right down the shaft. Of course, that limits your distance somewhat.
If you are using sights, having the arrow closer to your eye is not a good thing unless you use only one pin. The farther away from your eye the arrow is, the more distance (pins) you can access.
Most. . (all ?) Olympic archers are using sights and are shooting out to big distances. Think about it. . If they anchor with three under, close to their eye, they would not be able to hold the pin on the target after maybe 30 yards, if that. That doesn't help them.
In days gone by (when I cared about target archery ) the typical target anchor was under the chin, which allowed the string to touch the chin, the tip of the nose and split the aiming eye. All good things for lining up the same every time, as well as for giving a lot of room for pins.
As above, there is a difference in the way bows are tillered, 3 under and mediteranean ( split), but most will not tell the difference.
ChuckC