Query plans with MSTVFs in them don't include time populating the table variable
Imagine if you will, that you're using a multi statement table valued function. When you run a query that calls it, it may run for a very long time, but when you look at the operator times in your query plan, the time spent in the MSTVF isn't anywhere obvious.
The time will show up in the plan properties as elapsed time, so it is associated with the query somehow. I think it would be beneficial to present the time spent in the function in the TVF operator.
Henrik Staun Poulsen commented