Since their TURBOJET engines were not "spooled-up", the pilots have reported that they "applied thrust" -- but that was their misperception [their engines never accelerated off the earlier "stabilized thrust"].
Depends how you define the term "spooled up." Regardless of the low drag approach concept, the engines (the 737 series CFM 56) would usually be around 50-55 percent N1 right down to the flare. If the pilot closes the thrust levers on late final because he is too high or too fast, then by definition the aircraft is now not in a stable approach condition and the pilot should go-around. The CFM 56 has different spool up characteristics than the JT8D series engines on the 737-200 and indeed the CFM engines spool up faster. The B737 FCTM does not mention a minimum N1 in relation to an approach to land and this suggests there is no minimum N1 subject to an individual company designated figure. That figure might just be a guesswork number based on someone's personal whim rather than a manufacturer's figure.