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.