Hmmm...

I'd be curious about the flat resistance. Say one picks up a nail or a screw or a radial tire wire, or even a piece of glass. Will the tube be strong enough to push the damaging item back out? If so, why not build that technology into the tire itself? Would the shard of glass simply keep wearing until it finally cuts through?

I suspect if say you put one TPU tube in the rear, and one butyl tube in the front, the number of flats would be similar.