Don't know how the running group in CBD area behave. But the running group who I met very regularly along the Punggol Waterway PCN is more considerate. The Punggol SAFRA Running club. When they are in a big group, and saw me coming in the opposite direction, they will called to their fellow runners to keep single file and left.
Some areas in CBD are tight, already solo or 2-3 grp cyclists vs pedestrians got slight friction, but vastly ok if the cyclists are experienced enough, just mere inconveniences coz gotta change direction a bit. For me i always train ultra low speed / nearly track stands at Merlion area vs big group of tourists so no issue. lol

The most pro are the mountain/fixie bikers, mountain bike usually pop wheelies at Helix bridge amongst groups of clapping (ang moh) tourists, good ones can sustain the whole length of Helix bridge.

The fixie guys will do Superman, Spiderman, stand on the saddle or those stuff.
Big groups of 50-100 of coz will always be the worst off. Not possible to do single file, which IMO should be the norm at those areas, same goes to cyclists, Too big at those areas which are already tight.
If got human wall of 3-5 pedestrians walking "horizontally" along the path at SG river/MBS/GBTB/Bay Garden East, no problem also become problem. And that is not super rare, nearly every night i will come across one.