In the wake of the Davina and Dean cheating scandal on Married At First Sight, the hit reality show's relationship experts came under fire for not acting earlier.
John says it's not their job to do so.
"They [the couples] have round-the-clock psychologists to look after them," he told TV WEEK in Australia. "If they have needs in that respect, they have full access."
He explains they keep a close eye on the couples, hoping they'll flourish. But as we've seen, that doesn't always happen.
"It's really hard to watch at times," John says.
Fans have also been quick to question why Dean, 39, and Davina, 26, weren't matched from the start. After all, it would have saved a lot of heartache.
But John says the trio didn't view Dean and Davina as having "any potential whatsoever".
"Dean is strong-minded, outspoken and likes to take the lead in relationships," John explains. "We really wanted someone who could fit in with that.
"Tracey was that person. Davina is a firecracker – very volatile. Her communication style is blunt. She isn't interested in having someone take the lead."
But John says there was one thing he noticed about Dean and Davina as he watched their affair unfold.
"They had a very sexual side to them," he says. "I think that initially dragged them in."
John adds Davina was matched with Ryan because he's the physical type she wanted. They're also both sociable, into fitness, and Ryan says what he thinks.
"But their fight style became very toxic very early," he says. "It derailed them."
After Dean rejected Davina, viewers watched in disbelief as she tried to win back Ryan, but failed.
John says it's great that Ryan held his own.
"He's got boundaries and principles," he says. Speaking of the reunion episode he praised the "very honest, no-holds-barred Ryan" we saw.
But John admits even the experts were shocked by what went on between Dean and Davina.
"We'd never seen anything like this on MAFS before," he says. "Previously, if people weren't happy with their matches, they left. It's highly unpredictable."
He says the trio really wanted to see the couples succeed.
"We put in time and effort, and we believe in the matches," he says. "So when they're doing these things, we have that urge to want to say, 'Stop, commit, change, adjust here.'"
Sadly, now that the show has ended, not a single couple has survived the experiment, with John and Melissa being the last couple to announce their separation.