Suppose: I sent you the money, you call the shipping guys and notify them that it's time to ship the goods. That's all.

I don't see why the shipping company needs to verify anything themselves - they just need a call from the owner of the goods directing the shipment.

I don't know either, but usual shipping is FOB - freight on board, so the seller pays half of it. And so the seller typically doesn't do shit until the money is there.

And when it comes to trade between untrusted parties, it starts slow. To build trust.

Though crypto is great to making faster payments, that's sometimes an issue, and it can save the seller from the buyer's scam, but on the other hand completely exposes the buyer to the seller's scams. (Because cryptocurrency transfers are non-reversible usually [as in ever, except with a hard fork].)