Thanks. I guess I was making too much of it. On the hat site in the link, I noticed that some of the kepis were labeled as "chasseur style". Other were not. I thought it might have something to do with the stitching or the shape of the bill or who knows what.
I do see changes in some details of lots of caps. For example, some bills rounded and others pretty straight across the front. On some, the top seems to sit...well...on TOP, while on others the sides seem to curl over to a recessed top disk. I never understood why the details weren't all standardized, but I suppose it's because of various manufacturers.