There is a small subset of folks who are super efficient in creating ketones and burning them. Luis Villasenor of ketogains fame is a classic documented example. A blood meter tells you what is in the tank, but not the rate at which it's filled and emptied. If your body is really efficient at creating and burning Ketones, it will create a good balance within your body.
More studies need to be done in this area to see what factors pertain to this and if you can change it.