Italianinfrance Correct, well spotted. Direct line to THR is of limited use for precise descent planning. Commendable desire not to be low for no reason, that is where birds and CFITs are.
After ATIS, I would enter the final approach point (FI03R or similar ). It is also a good exercise for verifying that the FMS waypoint is coded where the chart says so; the location might vary. It does not hurt to understand your box.
The above method also helps when on downwind and calculating the worst 'what-if-shortcut' scenario. Adjusting the math to match the intermediate approach altitude against miles to go is no different than working with the elevation.