Was at my favorite gun shop the other day and they have a pretty nice Savage 99 take down, in 300 Savage, in the consignment rack. Looking at it I was reminded of the one I had and I also had the .410 barrel for it. But looking at 10Glocks choke tube from using TSS, I'm sure that barrel would look the same if TSS was used in it. Another one that went down the road to get something else that I no longer remember....
So there is a correct understanding, only the choke tube has signs of wear, and only about 1/2 of the parallel portion. 2/3rds or more of the tube has no signs of wear. I suspect it's the porting that is grabbing the shot cup and allowing pellets to get out ahead of the shot cup and make contact with the choke tube. There are no wad stripping rings in the Indian Creek .410 tube like there are in the 20, 12 and 10 gauge tubes. But the porting must be doing the same job. I've shot the same TSS loads out of the OEM flush FULL tube and through a Carlsons .385 TSS tube without porting and there are no signs of pellet contact like there is in the Indian Creek.
I've only shot Federal Heavyweioght TSS with the flight control wad. I've recovered several wads and note they are pretty thick walled and fairly stiff plastic. They aren't split to the end like traditional shot cups and only have slits in the middle, presumably to let it expand to fill the bore (but in thruth, I don't know when that mid-wad expension occurs). Whatever, it seems to protect the bore very well.
Here's a 12 gauge wad I shot out of my Benelli: