The F-15STOL/MTD was a tech demonstrator and was never supposed to be anything close to a production aircraft. The idea was to see if concepts for STOL performance were feasible on a fighter, as the Air Force was afraid for quite a while that a few well-placed strikes on airfields could knock out huge portions of a theater's air power by knocking out the runways. This thinking played a heavy part in the original ATF requirements - the F-22's thrust vectoring came from the STOL requirements that were dropped just before the prototypes flew, not because of agility requirements. The STOL/MTD demonstrated that a three-surface aircraft with thrust vectoring could get some absurdly short takeoff rolls while still being a viable combat aircraft, as well as the kind of supermaneuverability we've come to expect from three-surface thrust-vectoring aircraft.
However, the Air Force never had any serious plans to implement these features on production F-15s - it was more a testbed for the ATF program. Even if they did want to implement the features, the Gulf War would largely kill the STOL meme, as we found that even the most perfect strikes on runways were being repaired about as fast as we could bomb them.