The 'issue' with over-wing engine inlets is the fact that the high angles of attack used for STOL operations often shrouds the inlets causing diminished performance at a minimum to complete compressor stall and flame out at the worst.
Most STOL designs have inlets mounted forward of the wing to avoid this. However the exhaust of the engine is beneficial to be run over the wing as it can be used to create lift without actual airflow over the airframe.
Here are two versions of the Antinov AN-72/74 which is an STOL design. The AN-72/74 is the version with the forward mounted engines that exhaust over the wings and the more conventional pylon mounted engines below the wing is the AN-TK74-300 which gives up STOL in favor of increased range and reduced fuel burn.
As you can see Lockheeds design uses the best of both worlds, forward mounted semi-pylon mounted engines which are ducted to overwing exhausts to supplement the airflow over the wing to help increase the usable angle of attack before stall by accelerating the airflow at the back of the wing minimizing the possibility of flow separation.
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Originally Posted by kach22i
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