That's a very strange stove only a mother could love...
I dunno who designed that, but I cannot see the point of it. Corporate politics maybe.
Then you get the GS-340 - another weird beast, but it takes a quite different cartridge so I can't compare.
Anyhow, I am tempted to shrug my shoulders and ignore the strange fuel consumption figures, and believe those for the GS-100.
Comment: they tried to kill off the GS-100 and GST-100 as obsolete, but customer demand seems to have restored them. Amusing.
> Is this higher fuel consumption typical of inverted canister stoves?
No, but the answer is a shade more complex.
You see, you can shut an upright canister stove off immediately by closing the valve, but when you close the valve on a traditional inverted canister arrangement you still have the fuel in the line, and that can be wasted - unless you anticipate and shut down just a shade early.
If you run a series of tests wasting the fuel in the line each time, then you may get slightly greater fuel consumption.
> they only approve isobutane/butane canisters for use with their inverted stove and
> not the more expensive isobutane/propane canisters.
That's the lawyers springing into action. IGNORE! You can use ANY screw-thread canister. Just never let the canister get too hot to touch.