Model One does not even support Monero. I doubt it will handle Coin Joins properly. It seems like it can pretty much only handle the very basics before its hardware throttles.
You are right and I was thinking the same thing, but I was not expecting ancient Trezor One device to be
one trick pony 
If I was in Trezor team I would make new device with similar price (code name Trezor2) that could do everything like Trezor model T but in same old Trezor One package.
This should be possible with upgraded processor and small design changes, but I would still keep Trezor One active for firmware updates.
I think this new Trezor model R is going to be their new generation wallet with their own secure element, and I am sure it's going to be much more expensive than current wallets they are offering.
Even though it makes sense from a development and financial point of view they focus in the news generation, some people (like me) spending over 200$ for a cold wallet is a bit out of the budget...
I could agree with you few years ago, but with raging inflation and increased prices of everything we saw in last few years, $200 today is not the same like $200 few years ago.
And if someone is holding several Bitcoins than I see no reason why this amount of money would be such a big problem, but then again I always remember this meme:
EDIT:
Dates and times for Trezor CoinJoin testing are:
- February 15, 15:00 UTC
- February 22, 17:00 UTC
