The game clock was showing 19 minutes and 54 seconds remaining in the match and Walker and Koroisau had received their marching orders when there was 28 minutes and 13 seconds left, presented his stopwatch, which showed that the full 10 minutes had elapsed.
No such practice exists in the NRL, where a timekeeper from each team often using stopwatches are responsible for sending players banished to the sin bin back on the field.
The NRL has shot clocks for line dropouts and scrum re-starts which can be viewed by crowds inside a stadium, but there is no such easily identifiable countdown for sin bins.
It comes as both the NRL and Storm remain at odds over who was policing time spent in the sin bin for the four players who fell foul of the referees in Melbourne.
Under normal NRL procedure, each club can provide a sin bin operator at every game to time stints on the sidelines before a player re-enters the field of play.
Manly didn't have a sideline sin bin operator at AAMI Park, which reverts the responsibility solely to the home team with an NRL ground manager monitoring the process.
While the NRL stressed on Sunday there was no sin bin assistant from either side - leaving the role to the NRL ground manager - the Storm privately insist its football director Frank Ponissi was nominated for the role on the night.
Melbourne officials had been stunned to see Koroisau appear on the sideline and be given the all clear to enter the field of play before the 10-minute period had elapsed.
Ponissi raised the alarm immediately, racing over from the hosts' bench to alert the NRL's Melbourne-based match-day official Matt Hicks to the fact that Manly still had nearly another two minutes to serve with only 11 players.
The game clock was showing 19 minutes and 54 seconds remaining in the match and Walker and Koroisau had received their marching orders when there was 28 minutes and 13 seconds left. Hicks, however, presented his stopwatch, which showed that the full 10 minutes had elapsed.
It was unclear whether the official had forgotten to stop his watch while a video review was taking place to confirm a try to Manly's Akuila Uate in the 58th minute while he was confirming Wright could replace Walker, who was undergoing a head injury assessment.
But the Manly pair were given the all clear to run on and it was too late for Ponissi and Melbourne, who were keeping time themselves, to do anything about it.
Having lost the game by 20 points the Storm were not blaming their defeat on the cock-up and were reluctant to crucify Hicks for the mistake.
However, they were left scratching their heads about why the NRL did not have a better system in place to ensure players spent the correct time off the field when sin binned.
Some have argued a simple solution would be to rely more on the game clock as the gauge, allowing players to return when 10 minutes has wound down on it rather than leaning on stopwatches and having to factor in stoppages.