NRL head of football Graham Annesley has staunchly defended his match officials over "quite unfair" claims of inconsistency when punishing foul play.

There was controversy aplenty in round six leading to questions about why some indiscretions were treated differently to others in the past.

Among the talking points was Bulldogs forward Jack Hetherington becoming the first player sent off in 2021 for a swinging arm on Cowboys fullback Valentine Holmes on Sunday.

And Rabbitohs star Latrell Mitchell collected two dangerous contact charges and another for contrary conduct but wasn't so much as penalised for them against the Wests Tigers.

Annesley was unable to comment on those incidents in his Monday media briefing as the players had not yet decided whether to head to the judiciary, but he backed officials on a widespread scale.

"I think in many ways the criticism of consistency can be quite unfair because not every incident is the same," Annesley said.

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"There is a vast difference in some cases between the seriousness of incidents that take place on the field that the referees and the Bunker have to deal with. And that's reflected of course in what we ultimately see in the match review committee.

"The match review committee do sit around and take hours, rightly, to make sure we're getting these things as right as possible.

"It can vary anywhere to a grade-one charge resulting in a fine right through to a grade three charge or even a referral [to the judiciary] based on, in some cases, many, many minutes of discussion and debate amongst themselves."

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He noted the match review committee don't necessarily have to charge a player that has been placed on report, sin-binned or even sent off.

In demonstrating the many factors taken into account when punishing a player for foul play, Annesley referenced the game's rulebook showing the criteria.

And he argued it would be "unrealistic" to employ a blanket approach to punishing foul play, so naturally people would have conflicting opinions on decisions.

"Each of these instances are very unique, very different. There are degrees of force, there are degrees of circumstance," he continued.

"And the referees and the Bunker don't have hours to sit around talking about these decisions to determine what they're going to do.

"They might have five or ten seconds to make these decisions in some cases. And yet we're prepared to say they're inconsistent?

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"When they make a decision, I'm not stupid enough to suggest that everyone's going to agree with it.

"The great thing about our game and why it evokes the passion that it evokes and why so many people love our game is that people disagree over these things."

Meanwhile, Annesley said the frantic golden-point finish between the Rabbitohs and Tigers was proof of the Bunker being necessary.

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South Sydney forward Tom Burgess slammed the ball down to score a try – which was awarded on review - before Tigers halfback Luke Brooks picked it up and ran downfield to touchdown.

"For people who are sometimes critical of technology and [say] that it interferes too much with our game and slows our game down too much, how would the officials have been trying to make that decision without technology?" Annesley asked.

"It's just impossible. [It would have been] a big guess, literally a big guess by the officials.

"If they guessed and they guessed wrong and we saw footage like that afterwards, we'd be castigating the officials up hill and down dale."

Annesley also confirmed Melbourne did nothing wrong on Friday when they tactically used a free interchange to replace five-eighth Cameron Munster with Nelson Asofa-Solomona after a high shot from Roosters lock Victor Radley, who was sin binned.

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Munster went back on the field 30 seconds later having been checked by a doctor, swapping with Christian Welch, and the Storm had effectively rotated their props without cost.

"There's a bit of confusion that's been reigning about two different rules," Annesley said.

"The first is a rule that's been in our operational guidelines for probably the best part of a couple of decades. And that is about a free interchange if a player is injured as a result of foul play.

"So that means if a player is put on report, sin binned or sent off and the player who is the victim of that foul play comes off the field, they get a free interchange for that.

"That rule is not a new rule. It's been around for a long time ... What the Storm did in relation to that rule was legitimately within the rules," Annesley said.

Where the confusion has stemmed from, Annesley said, is the introduction of an 18th player, who can only come into the action if a teammate is ruled out for the match after foul play that resulted in the offender being sin-binned or sent off.