The heat output of a stove is a balance between the amount of fuel that can be delivered (white gas can be higher than propane or butane because there are more BTUs per unit of fuel and the fuel doesn't rely on heat from the environment for vaporization), the efficiency of the carburation (how much air can be drawn into the combustion process), and the surface area of the pot being heated (big pots allow bigger burners and more btus). I'm not an expert, but if there is a 10k BTU limit, it's probably due to the size of the fuel cannister.

For instance, they sell this adapter that permits you to "save" your BBQ event by attaching a disposable propane cannister if your refillable one goes empty. The only problem is that the BBQ doesn't get as hot because the cannister rapidly becomes quite frosty and loses pressure. The cannister doesn't have enough surface area to absorb the heat needed for the fuel to vaporize and produce the volume of gas required for the full rated output of the BBQ. I suspect that the amount of vapor that can be delivered on a typical 70-degree day is about 10,000 BTUs worth.

The boil time differences between stoves most likely are due to the methodology of the test. Unless identical conditions are present, boil times can vary quite a bit. What is the initial water temperature? What is the bottom surface area of the pot? How much water? What's the altitude? The ambient temperature? The humidity? Are they measuring to a simmer or a full boil? Is the water in the pot being stirred? Does the water have to reach 212F to be considered "boiling"?

Why not just be happy with the stove you bought? If it boils your water in a reasonable amount of time and doesn't weigh a ton, isn't that what really counts?