Unfortunately you didn't not pay directly via BTC.
You used coinbase, which is just as you would have used Visa, a 3rd party service.
So the title should be about Coinbase, Paypal and Visa, not bitcoin.
Nice article and congratulation for discovering merchant which accept
zero-confirmation 
Also, almost-instant transaction confirmation aka
zero-confirmation already used/accepted since few years ago even without SegWit.
It's not the merchant doing this.
It was Coinbase because he/she had already an verified account with them.