Hi North,
Altough I am not a MD-80 pilot, I think that not extending slats automatically from a clean configuration could make sense in a coffin corner context.
Imagine you are flying close to the aircraft celing at high speed and, due to any reason (turbulence, pilot error, etc.), speeds dropes down and the stall protection gets activated. If this automatically changes your configuration from clean to slats deployed at high mach speed, this could drive quite a serious issue, much more problematic than correcting a stall initiated at FL 370.