It is not odd, it is perfectly normal.
White Leghorns look alike because people culled all the ones that didn't match.
ISA Browns all look alike because they are bred to be that way: they are color-sexable at hatch IF the parents are the correct colors. So the hatcheries are careful about only using correctly-colored ones.
For the Whiting True Blues, if someone originally had chickens of a variety of colors but they all laid blue eggs, then selecting for just blue egg production would not make the feather colors any more consistent. The chickens would still have a variety of feather colors. The same is true of the Easter Eggers sold by many hatcheries: they select for egg color & production, but do not care about feather color, and the chickens come in a wide variety of colors.
If you wanted pure colors of the Whiting True Blues, you would have to get a bunch of the chickens, sort them by color, and then keep breeding each single-color line for quite a few generations, always culling the off-color chicks. (Some genetics knowledge can make it go a bit faster, but the basic process is still the same, and it will still take at least a few generations to get any pens that breed true for any specific colors.)