I have flown to Tioman a couple of times from Seletar airport. There are no duty-free shopping there, just check-in counter and Singapore customs clearance. Usually check-in and customs clearance are quite efficient because the planes are small and carry limited number of passengers. However, I can't say the same for the efficiency of the Malaysian customs clearance on Tioman. :sweatsm:
Taxi drivers seem to know the plane arrival times, for the few occasions where I landed on Seletar Airport, there were already taxis waiting outside.