The 18,000' TA in USA was my first solution to the 10,000' command in QRH. In USA it does not cause a problem. When I tried, via my training dept., to voice this question to Boeing and XAA's it was met with deaf ears. So there we are in the sim training something that is unrealistic and XAA's don't seem to care, neither did HOT. To be told it was WRONG to descend to FL80 was the last straw and confirmation that the loonies had taken over the place.
The USA might thing it rules the world. but not outside US airspace.