You have to differentiate between stick pushers and stick nudgers. Pushers were fitted to aircraft with serious stall problems such as the BAC1-11 to avoid a deep stall etc. Nudgers were fitted to a number of Boeing's and possibly other types, often for UK CAA certification, because they had a slight pitch up tendency before exhibiting a classic nose down pitch at stall. DP Davies did not like this slight pitch up as he states somewhere in Handling The Big Jets whereas the FAA accepted it given there was a natural nose down pitch at the stall. The nudger fitted on the 747 simply operated at the same time as the stick shaker and applied about a 5 pound push to the column to prevent the pre- stall pitch up.
DP Davies required about 20 Special Conditions for UK certificaton of the 747 but later CAA test pilots have vitrually eliminated them all.
Incidentally Boeing was horrified to find that airlines operating to UK CAA rules were stalling 747's on their air tests as they reckoned the wing wake buffet could take the horizontal stab close to its ultimate load and insisted a severe turbulence inspection be carried out after any stall. Eventually the full stall on the CAA air test was abandoned and the aircraft in my company were only taken to stick shaker onset.