Stewey, I wasn't trying to answer the QUESTION as such, but responding to what YOU said about it. When you referred to "the old days", I imagined you were referring to the 14th/15th centuries or thereabouts. My answer was simply pointing out that nobody had ever spoken/written about a 'round' of bread...as far as the record shows...before the mid-19th century.
Commercial bakeries already existed in that century; in fact Hovis were selling a million loaves a week before it ended. Accordingly, I guess we were beyond the days of bakers just chucking a lump of dough in the oven!
The obvious problem with doing that would be that, as soon as he placed the spherical lump on a baking-tray, it would flop down into a flattish, round shape. When it came out, it would be round, but - as people don't slice bread horizontally - the slices would be long and vaguely elliptical and far from round. Putting the dough in a baking-tin would produce slices even less round, as five of the six 'faces' would be flat!
As a matter of interest, the phrase 'round of beef' goes back as far as the 1600s. Clearly, a cylindrical joint such as a piece of leg would remain cylindrical even after cooking and thus produce round slices.
My overall point is that I do not believe the word 'round' in relation to bread or sandwiches can have anything to do with their actual shape, which was your point. But what the hey...I'm certainly not going to get into an argument about THAT!