He explains the difference here:

> I can pick up H417s on the official WCH store on Aliexpress with free shipping and no verification hullabalu.

I think the point is that anyone can make these chips, so there are Chinese sellers who just throw them in a padded envelope and send them out without bothering with all the stuff "serious" vendors do. And because they're cheap enough, if doesn't matter if some get lost in the mail.