Stall warning systems were not a feature on British aircraft, if Auster & Chipmunk were any guide. Fail to see why Tigers should have slats fitted, they were a buyers option after all. Military probably fitted them as a make work item for ab initio training, instilling cockpit check procedures. We had similar make work items imposed during ab initio, no flap landings if a flag was flying beside the runway van, canopy open at certain stages of flight, both for no good reason, other than to instil discipline.
The aircraft in the OP's link had slats, you can see the left plainly extended.
With only a little over seven hours in the Tiger, the pilot would have had little experience with the aircrafts characteristics, low power, high drag, small speed range, factors pointed out in the report. Was he even aware of the slats "clacking", I certainly don't recall it now from my nearly six decades ago experience, it certainly wasn't a subject of the endorsement.