So for the sake of science I decided to rip up my plum 13pro case. It had some damage to one of the corners and it was only $15 on woot so not a big loss. The leather is crazy thin! It’s like a sheet of paper. My guess would be they wanted to reduce weight because the 12 series added the bottom lip and the camera ring as well as the standard phones moving up to 6.1/6.7. They also had to add the MagSafe magnets.100% agree. They want it uniformed, so if they did go with multiple tanneries, they did something to make them uniform. I think @barecases might have been on to something saying they made them really thin. That would make them all uniform to an extent.
I truly believe they didn’t change the leather, but the coating they put on top. I think they heavily treated it with protection to keep the new look as long as possible. Clearly it’s leather and can’t stay like that forever, so it doesn’t age well at all. But it was all in the name of uniformity.