TL;DR(?)

• Shuttle scheduling has to coincide with the rest of KTM intercity for various reasons.
• Checkpoint flow has overlap on Singapore Immigration part, meaning arrival and departure can’t happen simultaneously. Only one at a time.
• KTM staff has to pass through checkpoint every time, accruing like 10 passport stamps per day.
• Sg’s K9 unit has to sniff every train even though it can’t physically go any further into Sg.
• Everything is a temporary stop-gap until RTS is operational, when the shuttle would be withdrawn and the checkpoint demolished.

There’s also a follow-up by writer on their ideas on how to speed up the shuttle to 30 mins.