Eh. Cognitive exercises don't hurt, even if the knowledge gained isn't particularly useful. Just because something is entertaining doesn't mean it won't stretch your critical thinking muscles.
I guess define "smart".
I guess define "smart".
But do any of the listed podcasts do that? To work a muscle or your brain, you have to actively...well, work. I haven't tried all of the podcasts they listed, but of the ones that I have tried, they're all passive entertainment. (And again, nothing wrong with that.)