are you sure about that ?
Reasonably sure... I'm not that familiar with the specifics of the NG - never really worked on it (I've spent most of my career working the Boeing wide-bodies). But our FADEC T/R thrust cutback logic is pretty much the same across all models, and we've had occasional issues with nuisance 'unlock' indications so cutting thrust just because the unlock light flickers could cause other problems. I'm also reasonably sure that on the 737 the "unlock" indication is a separate system from the FADEC thrust cutback position monitoring system.
If the light comes on during takeoff, the guidance on how to proceed would come from the FCOM/AFM.