Now Ryan, how can you say it is more natural to the bees? In nature the bees go out seeking a home. Some will find a hollow tree where the entrance location will only allow them to build above the opening, below the opening, or end up with the opening somewhere in the middle.
The bees may find shelter in a pile of rocks. Under a ledge, in tree branches, ahole in the ground, a cave,ect. With all the man made junk lying around it can be in gas tanks, water heaters, tires, discarded boxes, Use your imagination and that is where bees will build a home.
As far as the natural size of an entrance it can be small enough to allow only one bee at a time to pass, or up to the hive being out in the open.