Doesn’t the FMC add a fixed distance if the final fix has a heading after it and the next fix is behind you? Like a downwind from the east for landing to the east? Isnt it 30 miles??? So the FMC inputs 60(??) miles from the radar fix to the next fix on the approach?
That’s why understanding the FMC DTG (distance to go), planned/expected track miles, and straight line distance is good to know/estimate. Figure that out, add a dash of old school 3:1 math, add put the aircraft if the appropriate energy state (altitude/airspeed).
When in doubt remember ‘Tiger’ (*) errors will always allow you to get a bomb to a target but being a wimp just puts yourself at risk.
“We might be high but at least we’re fast.” :-/
* - tiger errors - fast, steep, high.
slow, shallow, low can put you in the frag envelope.