Tried out "Grabshare Wait" from SIN T2 to Kallang area hotel. S$11 for one person.
You wait "up to 3 minutes" for Grab to determine a share candidate. 1-2 riders on your request only.
I waited about 3 minutes. Driver showed up maybe 3 minutes later. We picked up another rider who had confused SIN T4 with T1

, then drove to drop me off first.
Verdict: faster than S$9 door to door shuttle where it's unpredictable where in the passenger order you'll be dropped off.