It depends if they’re part of the same dealer network that you got your defender.
Dealers normally allow any behavior that can make them money. If your trade in makes them money and your vehicle sale makes them money they’ll do whatever.
But the folks that sold you the Defender seem to like losing money. So who knows.
I have taken trade-ins where the trade-in is worth more than the car the client is buying. A dealer won’t care if the car you are trading is worth the same as the car you are buying.
Dealer side no issue. Actually might be a blessing for them depending on the unit.
Customer side maybe depending on the dealer. The might magically have run the numbers with the inventory specialist and now the tundra is worth less in trade to them.
My father owned a dealership. I remember them trading in campers, boats, snowmobiles and trailers of various types.
When my grandfather owned the business before that, they did a lot of service/repair work on “house credit” (they’d mail you a net 30 invoice after you picked up the car, and start charging interest on balances left unpaid after a month.).
The Yamaha trumpet I played in school originally came into the family when a customer insisted he take something for a repair bill for which they had no hope of ever repaying.