Odd that a Singapore Immigration officer was concerned. I have done u-turns on a 212 Sosbud multi-entry in KL and never had an issue.
I've even talked to Jakarta Immigration about the absurdity and how much money his Dept. could make by reforming this and permitting multi-entry foreigners to leave Indonesia at the International departure, go down to International arrivals and re-enter........for a price. No response
The changes that Atlantis refers have still not been implemented....we still await.