Tell him about Enhancer for YouTube Chrome Extension, it can go past 2x.
https://chromewebstore.google.com/detail/enhancer-for-youtub...
https://addons.mozilla.org/en-US/firefox/addon/enhancer-for-...
And I totally agree with your son, YouTube and Podcasts are sometimes just slow or waste time with irrelevant/boring information, and changing the playback speed is a highly underrated way to deal with it. You do get used to 2x after a while.