For your 3 examples, I clicked on "Explore the store" and of the dozen or so random items I clicked on, it was 1 to 3 days delivery. I also found a wooden cutting board that you could personalize with a customer name (laser etching) and that was 3 to 6 business days.
I didn't see any item that said 6 weeks for delivery like Etsy has.
The Princeton Audio article didn't specify but I'm guessing[1] he's using one of these 2 Amazon partner programs:
1) https://vendorexpress.amazon.com
2) https://www.amazon.com/gp/launchpad
This gets you a special Amazon products page with the cachet of "Ships from and sold by Amazon.com" which is more valuable than "Fulfilled by Amazon." Those programs are not appropriate for 2 month lead times.
[1] PA's dedicated Amazon product page which you can no longer reach from Amazon search but Google still had a link: https://www.amazon.com/Princeton-Audio-Site-Tonewood-Bluetoo...
I have a friend who works for a company that is a supplier for Amazon and Home Depot. He says they are both equally demanding and inflexible. I think that's just the game when being a supplier for big box inc. And obviously Princeton is not a big box product.
I'm no Amazon Homemade expert, but there are plenty of items that say they take time to make:
* Usually takes between 21 and 30 days to create
https://www.amazon.com/Live-Edge-Dining-Conference-Table/dp/...
* Usually takes between 21 and 30 days to create
https://www.amazon.com/Omondi-Odhuno-Originals-Traditional-M...
* Usually takes between 21 and 30 days to create
https://www.amazon.com/Heroic-Bronze-Sculpture-Statue-Fraser...
* Usually takes between 21 and 30 days to create
https://www.amazon.com/Abstract-Metal-Sculpture-Aircraft-Alu...
* Usually takes between 21 and 30 days to create
https://www.amazon.com/Stained-Glass-Window-Herons-sunset/dp...
...although I didn't find anything over 30 days, FWIW.
Because on the seller's page when data-entering the product's details, the maximum value allowed is "30 days". Princeton Audio wants "42 days".
Also, none of your examples have the valuable imprimatur: "Ships from and sold by Amazon.com."
PA wants a combination of "audience reach" + "flexible logistics" that Amazon doesn't currently offer.
But there is Amazon Handmade (which is supposed to be the Amazon Etsy):
https://services.amazon.com/handmade/handmade.html
...and Amazon Custom:
https://services.amazon.com/custom.html
..and Amazon Fine Art:
https://www.amazon.com/b/?node=6685269011
...so it looks like Amazon has their hands in other areas besides distribution of mass manufactured parts.