The talent contest's new 'all-stars' version, which sees former contestants return to compete again, was officially announced in June.
At the time, Susan was the only act bosses confirmed would be appearing - but she later pulled out.
A few weeks ago, reports revealed that the Scottish singer's busy schedule left her unable to take part.
While you might expect Simon to be miffed about The Champions losing BGT's biggest star, he actually thinks her exit could benefit the show.
The Syco chief told Lorraine that he now wants to reserve Susan for a potential second series of the spin-off.
"Truthfully, I didn't really know, but I do now, who was gonna be on the show," he said. "But Susan I knew about.
"I don't think she should have done it this year. She did AGT: Champions (America's Got Talent).
"I hope that if this does well we'll do it again next year and it'll become an annual event. You've gotta save something!"
Simon had already expressed a desire for future series - although he's clearly not holding back too much.
This year's line-up include no less than eight of BGT's thirteen previous winners.
Meanwhile, with the competition tougher than ever, it seems there's been soe tension between the judges.
Simon teased a tiff between Amanda Holden and Alesha Dixon amid one of the performances.
"I think Alesha and Amanda in particular last night… credit to Alesha, you were on fire last night," he smirked.
It's not all drama, however, as David laughed: "There's a lot of sexual tension - but not in the way you might imagine!"
Not only do the BGT favourites compete with each other on The Champions, they also face standout acts from international versions of Got Talent.
In each of five heats, the arena audience votes one contender through to the grand final, while another goes through from the Golden Buzzer.
Britain's Got Talent: The Champions begins this Saturday (31st August) at 8.00pm on ITV.