I must admit, I'm very surprised by the success he's having with the TinyPICO. I would never have guessed there is such a large market of amateurs in this niche who are experienced enough to know what they want yet lack the skills to know how to do it themselves (in an age where any hobbyist can order a fully assembled custom PCB from China for pennies!).
With that disclaimer, I mean no disrespect when I say this is a very basic design that I'm sure myself and any other experienced hobbyist or professional could whip up in an afternoon. There's nothing new or innovative here. It's small, it doesn't make any glaring errors in terms of low power design and... Well, that's about it.
Slap on the cheapest components you can find on LCSC and you've got a roaring success. It's disappointing how low the bar is, electrically at least.
He does, however, hit the nail on the head with design, networking, presentation, etc. There's even a devoted community that has grown around this board, who would swear to you it's the best thing since sliced bread.