I suspect you may be conflating two different things here.
Singapore Airlines offers "Singapore Stopover Holidays" to passengers transiting Singapore on Singapore Airlines flights only. These include hotel nights and airport transfers and are not free, although you usually get a good deal on the rates.
They also offers "free" stopovers in Singapore, which means that if it costs you (say) $2000 to fly London-Singapore-Sydney direct, you can add a break of a few days and still pay the same $2000. But in this scenario, hotels and transportation are your own problem.