They are a solid red oak.
It is rounded off.
They are not solid treads to begin with but several pieces all glued together. I have found this to be true not only from Home Depot but from high end flooring and stair suppliers as well. This I understand is for durability and longer life as a single board is more likely to split. The simple answer is that the bullnose is glued but might also be part of a wider board as I believe the stair tread is glued up and then the bullnose is milled on the edge. Mine are holding up very well.
If you look at the photo I would say it is an accurate representation. The treads I received have 4 joined boards plus the return. There is a grain change on each board and there is a noticeable color change with each board. The original treads on my stairs from 1950 have two joined boards, there is the tread edge with the bull nose of about 3 inches and the remaining tread is one piece. The pieces are high quality, but today you would pay a premium for less joins and more consistency.
Watt is the total length adding a return thread
The tread is the same on both sides, so you just flip it for a right or left return.
not routed at all noses are glued on
Good news! The 60" are back in stock and should be available to you by the end of the day.
I do not believe you have to size up. My tread was slightly over 48". Hope that helps.