Matt Roller is an assistant editor at ESPNcricinfo. @mroller98
"I think it makes us stronger," Swann, a three-time Ashes winner during his England career, said. "Which is hard on Jack, because he was doing a good job with the ball. But it extends the batting, which is important. And with all their lefties [Australia are expected to pick four left-handers in their top seven] we've got an offspinner bowling at them."
Leach has thrived under Ben Stokes' captaincy but has struggled against left-handers throughout his Test career. "Jack does a similar thing every game: he holds an end up and does a job," Swann said. "There are still areas I think he could be better and he does things differently to how I did, but he's playing a role in a team.
"If you've got seamers who are attacking all the time - if you've got Stokesy's bouncer theory coming in - then you need a spinner who can go around three an over rather than one going at sixes. It is a loss, but you've got Mo, who extends the batting... and they've got so many left handers."
Moeen's recall was confirmed by the ECB on Wednesday morning after discussions between him and Ben Stokes, Brendon McCullum and Rob Key - England's captain, coach and managing director respectively - over the past few days.
"The very fact that Baz and Stokesy are in charge makes it easy for him," Swann said, speaking at the launch of IG's Net Gains campaign at Lord's. "They've said, 'You come in and all your positive attributes are what we're after' - none of the hang-ups of anything that has happened before.
"I'm sure he's just been given a licence to run up and bowl, and spin it as hard as he can, and bat the way he can. I'm glad to see him back: he's still brilliant. I watched him in the IPL. He's mercurial, sure, but he's still a brilliant talent.
"I think having his tyres pumped up by Baz and Stokesy and coming into a dressing room with guys he has grown up with, who play in the same free-spirited way, will suit him down to the ground - and that is why he's come back."
Swann believes that Moeen's biggest challenge will be getting to grips with the red Dukes ball again, rather than the rhythms of first-class cricket after an absence of nearly two years. "They don't worry about that," he said. "They are redefining red-ball cricket and I applaud that.
"My one concern is the difference between bowling with the red Dukes ball and the white Kookaburra. There is a major difference. It is harder to bowl with a red Dukes ball: it is not as easy to grip, it is smaller.
"That might be an issue, just getting enough overs under the belt to be confident. The red ball can be almost slightly greasy: it has a wax on it and can be a bit tricky to get used to again. But if the sun is out and it's dry, that's no issue."
Swann also believes that Moeen's success - and his own - exposes an issue with English coaching of fingerspinners. "The reason why I always liked Mo as a bowler is because he spins it properly and bowls it off the right knuckle," he said. "He doesn't do it how you are coached in England, which goes back to why we haven't got many spinners.
"The coaching manual is wrong from an early age, for bowling spin. Mo is a natural spin bowler. I was a natural. Monty Panesar was a natural. We all hold it completely differently to how you are taught as a young kid: they teach you to put it [the ball] between the first knuckle on both your first and second finger as if you are opening the door which gives you no revolutions, no dip, no spin.
"You hold it on the first knuckle of your first finger and the second knuckle of your second finger and you rip it over the top. That is how you get high revolutions and drift and dip. That's how the Indian spinners bowl, when I watched them growing up, so I copied them. But you're not coached that in England."
To that end, Swann has launched a coaching career over the last 12 months. He was part of Trent Rockets' backroom staff in the Hundred last year, which they won, and said that he "adored" the opportunity to work with some of the best young county spinners on Lions tours to the UAE and Sri Lanka over the winter.
But he suggests that the wider message sent by Moeen's recall is "concerning". Swann said: "We haven't got 10 candidates lined up and banging on the door. it says that we don't have good enough spinners in the country ready to go.
"We have spinners coming through: I've been with the Lions and there are some talented lads there who I don't think personally are quite ready for Test cricket… someone like Jack Carson at Sussex is a great little bowler. I think he'd do well - but whether has has got the actual skills to cope with it is another thing.
"It could ruin a career before it has even started, so I think Mo is a safe - and exciting - option. And the fact he is there means Keysy and Baz are probably laughing that they had a back-up option there all along."