normal, similar set up with other manufacturers too. T135 / 80D17 - it's a temporary spare, not for constant use. If you check the actual diameter vs your proper tires, you will probably find there is very little difference.
For example (for which I am familiar with), the 2020 Soul comes with 16" - 18" tires depending on the model, but there is only one size compact spare T125 / 80D16