This sounds like it may be the problem...Is there a place where I can read more about this? Is it a known Trezor oddity
There is no data you can read as a source.
I learned this because I experienced the same thing with different coins.
It just has nothing to do with BTC.
There was dogecoin in the wallet.
I sent some of it to the stock market.
Then I looked and it showed the remaining dogecoin in my Trezor balance.
But there are no doges that need to be included in the exit address.
In other words, the system created a new doge address and sent the remaining balance there.
You can collect coins at a single address in Trezor, and you have to pay a fee for it.
However, when you send it, it warns you that this account belongs to you.
It warns you that you are sending it to yourself system