Using the await keyword in C# a TaskCanceledException will be thrown automatically regardless if you check it or not, it just won't stop your code once running the task starts, it checks before start and at the end to set the task and sets to a canceled state which leads to an exception.

Rust seems to just have exceptions you can't catch (Panics) they are like ThreadAbortExceptions in .Net. That is if task threw ThreadAbortExceptions instead of TaskCanceledException and you called await with an already cancelled token you would get similar behavior it seems.