Both the Galaxy S9 and S9+ phones shipped with 720p 960fps slow motion capability but the recording was limited to 0.2 seconds which is just too short a time span. This made it difficult to capture things in manual mode since the reaction time of your finger is about the same as the recording time making you miss moments. Pre-record made it easier but still limited to just 6.4 seconds playback in regular 30fps video timelines.
The new S9 update allows for manual high-speed recording to be used in 480fps slow motion mode at 720p for now 0.4 seconds or twice the recording time. This allows for easier capture of moments but in real time playback at 30fps it is the exact same playback time of 6.4 seconds. Since only 192 frames are recorded in the 0.4 seconds same as in the 960fps mode of 0.2sec then the only thing you gain is double the time to capture the moment. It would have been ideal to get also double the playback time. Memory buffer seems to be the limiting factor here!