The in-game flight planner in the World map has more bugs than & lamp-post in the Amazon, but I’ve discovered a weird glitch:
Load a flightplan (compiled in Simbrief), & the sim will assign the wrong approach or departure every time, without fail.
So, load the exact same flight plan again, & the result, the flight plan more closely matches the one you loaded in the first place, & wont contain erroneous approaches.