framer
Basically yes. Engaging the INCR speeds switch will cause the stick shaker/pusher to operate at a relatively lower AOA than the normal preset value. Absent actual icing contamination, this would be a 'false' warning of an impending stall. I believe this is almost certainly what happened. Thinking of it another way, if someone had thought to turn off the INCR speed, the stick shaker would have quit - problem solved.