I'm glad this comment was here, it was the first thing I latched on to that seemed very specific to this person (or at least uncommon amongst general "podcast guys").

In particular, check out the pronunciation of the trailing S is the word "this" at 28 seconds in the clip of Davide Greene compared to 24 seconds in the Notebook LM clip. Really seemed uncannily similar to me.

He almost certainly doesn't "lisp" his S's if you heard him in real life, but says them perfectly normally.

What you're hearing is the way microphones deal with the hissing of an "s", same as they struggle with plosives like "p", from the whoosh of air. It's an artifact of microphones close to the mouth, so it makes sense that Google replicates it.

You can use physical pop filters or digital audio filters to reduce the effect, but podcasters don't usually use the physical ones, and the level of audio processing podcasters do really depends on their level of expertise and how much they even care.

When I was university, I got heavy into spoken word poetry and making hip hop. Personal Journals by Sage Francis had become a huge part of my life and rather than focus on school like a mature person I thought I’d make my own album. It turns out I have a profound lack of talent, but I got a lot of experience with a microphone.

To me that ‘s’ sound reminds me of the sibilance a Shure SM58 picks up without a pop filter. I hear a different side of the same idea on ‘p’ and ‘b’ as well.

I had a speech impediment as a youngster and the sound got in my head. Now I hear it on podcasts.