My coins all got placed in segwit addresses when I moved them to a new Trezor.
This.
that's it
Perhaps I should have worded it differently. I could have opted out of them going into segwit addresses. I simply did not. And so because I did not they were placed in a setwit address. Very sorry to have spread confusion and misunderstanding.

As noted above, Segwit is default setting on Trevor but you can open legacy addresses. You only get forced onto Segwit if you dont understand what you are doing.
Whether people who dont know what they are doing should be defaulted to Segwit is an interesting debate. I would be inclined to go with yes.
In my case I understood that I could have chosen a non-segwit address it simply hadn't occurred to me that there would be a good reason not to migrate to segwit. (I'm still not convinced there is except to those who are exceptionally paranoid)