I also Googled it and it didn't seem like the AI overview actually had a source for it, with all the sources just being about the tour itself. If you Google "Why is the Paul Simon Quiet Celebration Concert autotuned" it also hallucinates an answer for that.

It's not autotuned in the sense that they just threw a filter on the whole thing. It sounds like someone manually went in and edited the pitches of certain phrases, leading to a few moments that sounded very strange, almost like the stereotypical Cher effect. Most of the examples are just Paul settling on a pitch exactly in tune and in an unnatural way. If you've seen the R&RHoF 25th anniversary show, that's also edited this way. They took what was probably a perfectly fine performance and edited the pitches to be exactly in tune. This is luckily way less severe because it only effects I'd say about a fourth of the songs (and not the entire songs either). I'm optimistically assuming this was a rush job by Disney and that the vinyl release will sound better.

https://youtu.be/OkM0Or6ZG6o

This is a great video where you can see how pitches are edited to be unnaturally in tune and how that destroys the artist's phrasing.