Have to agree with Roger. Why not? In fact, I even think it's preferable to some silly "describe your typical duty day" language proficiency interview.
I believe the problem is "concentrating on plain language" tasks. Just fly the airplane (well, sim in this case). If the test is well constructed and integrated into the sim scenario, it should be non-obtrusive. By that I mean, during your debrief, you shouldn't really have any idea of how your plain language was tested. Your proficiency should have been measured just by your using it in the appropriate situations during the scenarios.
The ICAO "scoring" is in 6 areas. Comprehension is one that doesn't even require you to speak. Throw in as many strange accents and voices pitches on the ATC side. "Sim 12Alfa, turn left 260 immediate." Just as with a live controller in real life, if you turn to a heading of 260, your verbal response is unimportant. You passed your comprehension test item.
Plain language requirements don't mean you are necessarily capable of ordering a pizza in a country that uses the language. It means you can understand and be understood with minimal effort whilst driving the airplane.
Chill...you got enough to worry about with the LOFT scenarios.